diff --git a/MANIFEST.in b/MANIFEST.in
index 79e7891339..22cd7682aa 100644
--- a/MANIFEST.in
+++ b/MANIFEST.in
@@ -3,7 +3,7 @@ include README.rst
 include LONG_DESCRIPTION.rst
 include CODE_OF_CONDUCT.md CONTRIBUTING.md
 include test-requirements.txt
-include trio/py.typed
-recursive-include trio/_tests/test_ssl_certs *.pem
+include src/trio/py.typed
+recursive-include src/trio/_tests/test_ssl_certs *.pem
 recursive-include docs *
 prune docs/build
diff --git a/check.sh b/check.sh
index 01efd273db..a6f41a6d5d 100755
--- a/check.sh
+++ b/check.sh
@@ -13,7 +13,7 @@ fi
 
 # Test if the generated code is still up to date
 echo "::group::Generate Exports"
-python ./trio/_tools/gen_exports.py --test \
+python ./src/trio/_tools/gen_exports.py --test \
     || EXIT_STATUS=$?
 echo "::endgroup::"
 
@@ -23,10 +23,10 @@ echo "::endgroup::"
 # autoflake --recursive --in-place .
 # pyupgrade --py3-plus $(find . -name "*.py")
 echo "::group::Black"
-if ! black --check trio; then
+if ! black --check src/trio; then
     echo "* Black found issues" >> "$GITHUB_STEP_SUMMARY"
     EXIT_STATUS=1
-    black --diff trio
+    black --diff src/trio
     echo "::endgroup::"
     echo "::error:: Black found issues"
 else
@@ -57,16 +57,16 @@ echo "::group::Mypy"
 rm -f mypy_annotate.dat
 # Pipefail makes these pipelines fail if mypy does, even if mypy_annotate.py succeeds.
 set -o pipefail
-mypy trio --show-error-end --platform linux | python ./trio/_tools/mypy_annotate.py --dumpfile mypy_annotate.dat --platform Linux \
+mypy src/trio --show-error-end --platform linux | python ./src/trio/_tools/mypy_annotate.py --dumpfile mypy_annotate.dat --platform Linux \
     || { echo "* Mypy (Linux) found type errors." >> "$GITHUB_STEP_SUMMARY"; MYPY=1; }
 # Darwin tests FreeBSD too
-mypy trio --show-error-end --platform darwin | python ./trio/_tools/mypy_annotate.py --dumpfile mypy_annotate.dat --platform Mac \
+mypy src/trio --show-error-end --platform darwin | python ./src/trio/_tools/mypy_annotate.py --dumpfile mypy_annotate.dat --platform Mac \
     || { echo "* Mypy (Mac) found type errors." >> "$GITHUB_STEP_SUMMARY"; MYPY=1; }
-mypy trio --show-error-end --platform win32 | python ./trio/_tools/mypy_annotate.py --dumpfile mypy_annotate.dat --platform Windows \
+mypy src/trio --show-error-end --platform win32 | python ./src/trio/_tools/mypy_annotate.py --dumpfile mypy_annotate.dat --platform Windows \
     || { echo "* Mypy (Windows) found type errors." >> "$GITHUB_STEP_SUMMARY"; MYPY=1; }
 set +o pipefail
 # Re-display errors using Github's syntax, read out of mypy_annotate.dat
-python ./trio/_tools/mypy_annotate.py --dumpfile mypy_annotate.dat
+python ./src/trio/_tools/mypy_annotate.py --dumpfile mypy_annotate.dat
 # Then discard.
 rm -f mypy_annotate.dat
 echo "::endgroup::"
@@ -97,11 +97,11 @@ fi
 codespell || EXIT_STATUS=$?
 
 echo "::group::Pyright interface tests"
-python trio/_tests/check_type_completeness.py --overwrite-file || EXIT_STATUS=$?
-if git status --porcelain trio/_tests/verify_types*.json | grep -q "M"; then
+python src/trio/_tests/check_type_completeness.py --overwrite-file || EXIT_STATUS=$?
+if git status --porcelain src/trio/_tests/verify_types*.json | grep -q "M"; then
     echo "* Type completeness changed, please update!" >> "$GITHUB_STEP_SUMMARY"
     echo "::error::Type completeness changed, please update!"
-    git --no-pager diff --color trio/_tests/verify_types*.json
+    git --no-pager diff --color src/trio/_tests/verify_types*.json
     EXIT_STATUS=1
 fi
 
@@ -118,8 +118,8 @@ Problems were found by static analysis (listed above).
 To fix formatting and see remaining errors, run
 
     pip install -r test-requirements.txt
-    black trio
-    isort trio
+    black src/trio
+    ruff check src/trio
     ./check.sh
 
 in your local checkout.
diff --git a/ci.sh b/ci.sh
index e97bb68754..f808decdae 100755
--- a/ci.sh
+++ b/ci.sh
@@ -95,7 +95,7 @@ else
         # when installing, and then running 'certmgr.msc' and exporting the
         # certificate. See:
         #    http://www.migee.com/2010/09/24/solution-for-unattendedsilent-installs-and-would-you-like-to-install-this-device-software/
-        certutil -addstore "TrustedPublisher" trio/_tests/astrill-codesigning-cert.cer
+        certutil -addstore "TrustedPublisher" src/trio/_tests/astrill-codesigning-cert.cer
         # Double-slashes are how you tell windows-bash that you want a single
         # slash, and don't treat this as a unix-style filename that needs to
         # be replaced by a windows-style filename.
diff --git a/docs/source/conf.py b/docs/source/conf.py
index 5058c1bd51..af358abf15 100755
--- a/docs/source/conf.py
+++ b/docs/source/conf.py
@@ -22,7 +22,7 @@
 # For our local_customization module
 sys.path.insert(0, os.path.abspath("."))
 # For trio itself
-sys.path.insert(0, os.path.abspath("../.."))
+sys.path.insert(0, os.path.abspath("../../src"))
 
 # Enable reloading with `typing.TYPE_CHECKING` being True
 os.environ["SPHINX_AUTODOC_RELOAD_MODULES"] = "1"
diff --git a/pyproject.toml b/pyproject.toml
index 14c7f7794a..9caa39c3af 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -65,9 +65,6 @@ Changelog = "https://trio.readthedocs.io/en/latest/history.html"
 # doesn't look like a source file, so long as it appears in MANIFEST.in:
 include-package-data = true
 
-[tool.setuptools.packages]
-find = {namespaces = false}
-
 [tool.setuptools.dynamic]
 version = {attr = "trio._version.__version__"}
 
@@ -84,7 +81,6 @@ force-exclude = '''
 ignore-words-list = 'astroid,crasher,asend'
 
 [tool.ruff]
-target-version = "py38"
 respect-gitignore = true
 fix = true
 
@@ -92,7 +88,7 @@ allowed-confusables = ["–"]
 
 # The directories to consider when resolving first vs. third-party imports.
 # Does not control what files to include/exclude!
-src = ["trio", "notes-to-self"]
+src = ["src/trio", "notes-to-self"]
 
 select = [
   "RUF",  # Ruff-specific rules
@@ -124,13 +120,13 @@ extend-exclude = [
 ]
 
 [tool.ruff.per-file-ignores]
-'trio/__init__.py' = ['F401']
-'trio/_core/__init__.py' = ['F401']
-'trio/_core/_tests/test_multierror_scripts/*' = ['F401']
-'trio/abc.py' = ['F401']
-'trio/lowlevel.py' = ['F401']
-'trio/socket.py' = ['F401']
-'trio/testing/__init__.py' = ['F401']
+'src/trio/__init__.py' = ['F401']
+'src/trio/_core/__init__.py' = ['F401']
+'src/trio/_core/_tests/test_multierror_scripts/*' = ['F401']
+'src/trio/abc.py' = ['F401']
+'src/trio/lowlevel.py' = ['F401']
+'src/trio/socket.py' = ['F401']
+'src/trio/testing/__init__.py' = ['F401']
 
 [tool.ruff.isort]
 combine-as-imports = true
@@ -184,6 +180,7 @@ issue_format = "`#{issue} <https://github.com/python-trio/trio/issues/{issue}>`_
 # - At release time after bumping version number, run: towncrier
 # (or towncrier --draft)
 package = "trio"
+package_dir = "src"
 underlines = ["-", "~", "^"]
 
 [[tool.towncrier.type]]
@@ -228,7 +225,7 @@ showcontent = true
 
 [tool.coverage.run]
 branch = true
-source = ["trio"]
+source_pkgs = ["trio"]
 omit = [
     # These are run in subprocesses, but still don't work. We follow
     # coverage's documentation to no avail.
diff --git a/trio/__init__.py b/src/trio/__init__.py
similarity index 100%
rename from trio/__init__.py
rename to src/trio/__init__.py
diff --git a/trio/_abc.py b/src/trio/_abc.py
similarity index 100%
rename from trio/_abc.py
rename to src/trio/_abc.py
diff --git a/trio/_channel.py b/src/trio/_channel.py
similarity index 100%
rename from trio/_channel.py
rename to src/trio/_channel.py
diff --git a/trio/_core/__init__.py b/src/trio/_core/__init__.py
similarity index 100%
rename from trio/_core/__init__.py
rename to src/trio/_core/__init__.py
diff --git a/trio/_core/_asyncgens.py b/src/trio/_core/_asyncgens.py
similarity index 100%
rename from trio/_core/_asyncgens.py
rename to src/trio/_core/_asyncgens.py
diff --git a/trio/_core/_entry_queue.py b/src/trio/_core/_entry_queue.py
similarity index 100%
rename from trio/_core/_entry_queue.py
rename to src/trio/_core/_entry_queue.py
diff --git a/trio/_core/_exceptions.py b/src/trio/_core/_exceptions.py
similarity index 100%
rename from trio/_core/_exceptions.py
rename to src/trio/_core/_exceptions.py
diff --git a/trio/_core/_generated_instrumentation.py b/src/trio/_core/_generated_instrumentation.py
similarity index 100%
rename from trio/_core/_generated_instrumentation.py
rename to src/trio/_core/_generated_instrumentation.py
diff --git a/trio/_core/_generated_io_epoll.py b/src/trio/_core/_generated_io_epoll.py
similarity index 100%
rename from trio/_core/_generated_io_epoll.py
rename to src/trio/_core/_generated_io_epoll.py
diff --git a/trio/_core/_generated_io_kqueue.py b/src/trio/_core/_generated_io_kqueue.py
similarity index 100%
rename from trio/_core/_generated_io_kqueue.py
rename to src/trio/_core/_generated_io_kqueue.py
diff --git a/trio/_core/_generated_io_windows.py b/src/trio/_core/_generated_io_windows.py
similarity index 100%
rename from trio/_core/_generated_io_windows.py
rename to src/trio/_core/_generated_io_windows.py
diff --git a/trio/_core/_generated_run.py b/src/trio/_core/_generated_run.py
similarity index 100%
rename from trio/_core/_generated_run.py
rename to src/trio/_core/_generated_run.py
diff --git a/trio/_core/_instrumentation.py b/src/trio/_core/_instrumentation.py
similarity index 100%
rename from trio/_core/_instrumentation.py
rename to src/trio/_core/_instrumentation.py
diff --git a/trio/_core/_io_common.py b/src/trio/_core/_io_common.py
similarity index 100%
rename from trio/_core/_io_common.py
rename to src/trio/_core/_io_common.py
diff --git a/trio/_core/_io_epoll.py b/src/trio/_core/_io_epoll.py
similarity index 100%
rename from trio/_core/_io_epoll.py
rename to src/trio/_core/_io_epoll.py
diff --git a/trio/_core/_io_kqueue.py b/src/trio/_core/_io_kqueue.py
similarity index 100%
rename from trio/_core/_io_kqueue.py
rename to src/trio/_core/_io_kqueue.py
diff --git a/trio/_core/_io_windows.py b/src/trio/_core/_io_windows.py
similarity index 100%
rename from trio/_core/_io_windows.py
rename to src/trio/_core/_io_windows.py
diff --git a/trio/_core/_ki.py b/src/trio/_core/_ki.py
similarity index 100%
rename from trio/_core/_ki.py
rename to src/trio/_core/_ki.py
diff --git a/trio/_core/_local.py b/src/trio/_core/_local.py
similarity index 100%
rename from trio/_core/_local.py
rename to src/trio/_core/_local.py
diff --git a/trio/_core/_mock_clock.py b/src/trio/_core/_mock_clock.py
similarity index 100%
rename from trio/_core/_mock_clock.py
rename to src/trio/_core/_mock_clock.py
diff --git a/trio/_core/_multierror.py b/src/trio/_core/_multierror.py
similarity index 100%
rename from trio/_core/_multierror.py
rename to src/trio/_core/_multierror.py
diff --git a/trio/_core/_parking_lot.py b/src/trio/_core/_parking_lot.py
similarity index 100%
rename from trio/_core/_parking_lot.py
rename to src/trio/_core/_parking_lot.py
diff --git a/trio/_core/_run.py b/src/trio/_core/_run.py
similarity index 100%
rename from trio/_core/_run.py
rename to src/trio/_core/_run.py
diff --git a/trio/_core/_tests/__init__.py b/src/trio/_core/_tests/__init__.py
similarity index 100%
rename from trio/_core/_tests/__init__.py
rename to src/trio/_core/_tests/__init__.py
diff --git a/trio/_core/_tests/test_asyncgen.py b/src/trio/_core/_tests/test_asyncgen.py
similarity index 100%
rename from trio/_core/_tests/test_asyncgen.py
rename to src/trio/_core/_tests/test_asyncgen.py
diff --git a/trio/_core/_tests/test_guest_mode.py b/src/trio/_core/_tests/test_guest_mode.py
similarity index 100%
rename from trio/_core/_tests/test_guest_mode.py
rename to src/trio/_core/_tests/test_guest_mode.py
diff --git a/trio/_core/_tests/test_instrumentation.py b/src/trio/_core/_tests/test_instrumentation.py
similarity index 100%
rename from trio/_core/_tests/test_instrumentation.py
rename to src/trio/_core/_tests/test_instrumentation.py
diff --git a/trio/_core/_tests/test_io.py b/src/trio/_core/_tests/test_io.py
similarity index 100%
rename from trio/_core/_tests/test_io.py
rename to src/trio/_core/_tests/test_io.py
diff --git a/trio/_core/_tests/test_ki.py b/src/trio/_core/_tests/test_ki.py
similarity index 100%
rename from trio/_core/_tests/test_ki.py
rename to src/trio/_core/_tests/test_ki.py
diff --git a/trio/_core/_tests/test_local.py b/src/trio/_core/_tests/test_local.py
similarity index 100%
rename from trio/_core/_tests/test_local.py
rename to src/trio/_core/_tests/test_local.py
diff --git a/trio/_core/_tests/test_mock_clock.py b/src/trio/_core/_tests/test_mock_clock.py
similarity index 100%
rename from trio/_core/_tests/test_mock_clock.py
rename to src/trio/_core/_tests/test_mock_clock.py
diff --git a/trio/_core/_tests/test_multierror.py b/src/trio/_core/_tests/test_multierror.py
similarity index 100%
rename from trio/_core/_tests/test_multierror.py
rename to src/trio/_core/_tests/test_multierror.py
diff --git a/trio/_core/_tests/test_multierror_scripts/__init__.py b/src/trio/_core/_tests/test_multierror_scripts/__init__.py
similarity index 100%
rename from trio/_core/_tests/test_multierror_scripts/__init__.py
rename to src/trio/_core/_tests/test_multierror_scripts/__init__.py
diff --git a/trio/_core/_tests/test_multierror_scripts/_common.py b/src/trio/_core/_tests/test_multierror_scripts/_common.py
similarity index 100%
rename from trio/_core/_tests/test_multierror_scripts/_common.py
rename to src/trio/_core/_tests/test_multierror_scripts/_common.py
diff --git a/trio/_core/_tests/test_multierror_scripts/apport_excepthook.py b/src/trio/_core/_tests/test_multierror_scripts/apport_excepthook.py
similarity index 100%
rename from trio/_core/_tests/test_multierror_scripts/apport_excepthook.py
rename to src/trio/_core/_tests/test_multierror_scripts/apport_excepthook.py
diff --git a/trio/_core/_tests/test_multierror_scripts/simple_excepthook.py b/src/trio/_core/_tests/test_multierror_scripts/simple_excepthook.py
similarity index 100%
rename from trio/_core/_tests/test_multierror_scripts/simple_excepthook.py
rename to src/trio/_core/_tests/test_multierror_scripts/simple_excepthook.py
diff --git a/trio/_core/_tests/test_parking_lot.py b/src/trio/_core/_tests/test_parking_lot.py
similarity index 100%
rename from trio/_core/_tests/test_parking_lot.py
rename to src/trio/_core/_tests/test_parking_lot.py
diff --git a/trio/_core/_tests/test_run.py b/src/trio/_core/_tests/test_run.py
similarity index 100%
rename from trio/_core/_tests/test_run.py
rename to src/trio/_core/_tests/test_run.py
diff --git a/trio/_core/_tests/test_thread_cache.py b/src/trio/_core/_tests/test_thread_cache.py
similarity index 100%
rename from trio/_core/_tests/test_thread_cache.py
rename to src/trio/_core/_tests/test_thread_cache.py
diff --git a/trio/_core/_tests/test_tutil.py b/src/trio/_core/_tests/test_tutil.py
similarity index 100%
rename from trio/_core/_tests/test_tutil.py
rename to src/trio/_core/_tests/test_tutil.py
diff --git a/trio/_core/_tests/test_unbounded_queue.py b/src/trio/_core/_tests/test_unbounded_queue.py
similarity index 100%
rename from trio/_core/_tests/test_unbounded_queue.py
rename to src/trio/_core/_tests/test_unbounded_queue.py
diff --git a/trio/_core/_tests/test_windows.py b/src/trio/_core/_tests/test_windows.py
similarity index 100%
rename from trio/_core/_tests/test_windows.py
rename to src/trio/_core/_tests/test_windows.py
diff --git a/trio/_core/_tests/tutil.py b/src/trio/_core/_tests/tutil.py
similarity index 100%
rename from trio/_core/_tests/tutil.py
rename to src/trio/_core/_tests/tutil.py
diff --git a/trio/_core/_thread_cache.py b/src/trio/_core/_thread_cache.py
similarity index 100%
rename from trio/_core/_thread_cache.py
rename to src/trio/_core/_thread_cache.py
diff --git a/trio/_core/_traps.py b/src/trio/_core/_traps.py
similarity index 100%
rename from trio/_core/_traps.py
rename to src/trio/_core/_traps.py
diff --git a/trio/_core/_unbounded_queue.py b/src/trio/_core/_unbounded_queue.py
similarity index 100%
rename from trio/_core/_unbounded_queue.py
rename to src/trio/_core/_unbounded_queue.py
diff --git a/trio/_core/_wakeup_socketpair.py b/src/trio/_core/_wakeup_socketpair.py
similarity index 100%
rename from trio/_core/_wakeup_socketpair.py
rename to src/trio/_core/_wakeup_socketpair.py
diff --git a/trio/_core/_windows_cffi.py b/src/trio/_core/_windows_cffi.py
similarity index 100%
rename from trio/_core/_windows_cffi.py
rename to src/trio/_core/_windows_cffi.py
diff --git a/trio/_deprecate.py b/src/trio/_deprecate.py
similarity index 100%
rename from trio/_deprecate.py
rename to src/trio/_deprecate.py
diff --git a/trio/_dtls.py b/src/trio/_dtls.py
similarity index 100%
rename from trio/_dtls.py
rename to src/trio/_dtls.py
diff --git a/trio/_file_io.py b/src/trio/_file_io.py
similarity index 100%
rename from trio/_file_io.py
rename to src/trio/_file_io.py
diff --git a/trio/_highlevel_generic.py b/src/trio/_highlevel_generic.py
similarity index 100%
rename from trio/_highlevel_generic.py
rename to src/trio/_highlevel_generic.py
diff --git a/trio/_highlevel_open_tcp_listeners.py b/src/trio/_highlevel_open_tcp_listeners.py
similarity index 100%
rename from trio/_highlevel_open_tcp_listeners.py
rename to src/trio/_highlevel_open_tcp_listeners.py
diff --git a/trio/_highlevel_open_tcp_stream.py b/src/trio/_highlevel_open_tcp_stream.py
similarity index 100%
rename from trio/_highlevel_open_tcp_stream.py
rename to src/trio/_highlevel_open_tcp_stream.py
diff --git a/trio/_highlevel_open_unix_stream.py b/src/trio/_highlevel_open_unix_stream.py
similarity index 100%
rename from trio/_highlevel_open_unix_stream.py
rename to src/trio/_highlevel_open_unix_stream.py
diff --git a/trio/_highlevel_serve_listeners.py b/src/trio/_highlevel_serve_listeners.py
similarity index 100%
rename from trio/_highlevel_serve_listeners.py
rename to src/trio/_highlevel_serve_listeners.py
diff --git a/trio/_highlevel_socket.py b/src/trio/_highlevel_socket.py
similarity index 100%
rename from trio/_highlevel_socket.py
rename to src/trio/_highlevel_socket.py
diff --git a/trio/_highlevel_ssl_helpers.py b/src/trio/_highlevel_ssl_helpers.py
similarity index 100%
rename from trio/_highlevel_ssl_helpers.py
rename to src/trio/_highlevel_ssl_helpers.py
diff --git a/trio/_path.py b/src/trio/_path.py
similarity index 100%
rename from trio/_path.py
rename to src/trio/_path.py
diff --git a/trio/_signals.py b/src/trio/_signals.py
similarity index 100%
rename from trio/_signals.py
rename to src/trio/_signals.py
diff --git a/trio/_socket.py b/src/trio/_socket.py
similarity index 100%
rename from trio/_socket.py
rename to src/trio/_socket.py
diff --git a/trio/_ssl.py b/src/trio/_ssl.py
similarity index 100%
rename from trio/_ssl.py
rename to src/trio/_ssl.py
diff --git a/trio/_subprocess.py b/src/trio/_subprocess.py
similarity index 100%
rename from trio/_subprocess.py
rename to src/trio/_subprocess.py
diff --git a/trio/_subprocess_platform/__init__.py b/src/trio/_subprocess_platform/__init__.py
similarity index 100%
rename from trio/_subprocess_platform/__init__.py
rename to src/trio/_subprocess_platform/__init__.py
diff --git a/trio/_subprocess_platform/kqueue.py b/src/trio/_subprocess_platform/kqueue.py
similarity index 100%
rename from trio/_subprocess_platform/kqueue.py
rename to src/trio/_subprocess_platform/kqueue.py
diff --git a/trio/_subprocess_platform/waitid.py b/src/trio/_subprocess_platform/waitid.py
similarity index 100%
rename from trio/_subprocess_platform/waitid.py
rename to src/trio/_subprocess_platform/waitid.py
diff --git a/trio/_subprocess_platform/windows.py b/src/trio/_subprocess_platform/windows.py
similarity index 100%
rename from trio/_subprocess_platform/windows.py
rename to src/trio/_subprocess_platform/windows.py
diff --git a/trio/_sync.py b/src/trio/_sync.py
similarity index 100%
rename from trio/_sync.py
rename to src/trio/_sync.py
diff --git a/trio/_tests/__init__.py b/src/trio/_tests/__init__.py
similarity index 100%
rename from trio/_tests/__init__.py
rename to src/trio/_tests/__init__.py
diff --git a/trio/_tests/astrill-codesigning-cert.cer b/src/trio/_tests/astrill-codesigning-cert.cer
similarity index 100%
rename from trio/_tests/astrill-codesigning-cert.cer
rename to src/trio/_tests/astrill-codesigning-cert.cer
diff --git a/trio/_tests/check_type_completeness.py b/src/trio/_tests/check_type_completeness.py
similarity index 100%
rename from trio/_tests/check_type_completeness.py
rename to src/trio/_tests/check_type_completeness.py
diff --git a/trio/_tests/module_with_deprecations.py b/src/trio/_tests/module_with_deprecations.py
similarity index 100%
rename from trio/_tests/module_with_deprecations.py
rename to src/trio/_tests/module_with_deprecations.py
diff --git a/trio/_tests/pytest_plugin.py b/src/trio/_tests/pytest_plugin.py
similarity index 100%
rename from trio/_tests/pytest_plugin.py
rename to src/trio/_tests/pytest_plugin.py
diff --git a/trio/_tests/test_abc.py b/src/trio/_tests/test_abc.py
similarity index 100%
rename from trio/_tests/test_abc.py
rename to src/trio/_tests/test_abc.py
diff --git a/trio/_tests/test_channel.py b/src/trio/_tests/test_channel.py
similarity index 100%
rename from trio/_tests/test_channel.py
rename to src/trio/_tests/test_channel.py
diff --git a/trio/_tests/test_contextvars.py b/src/trio/_tests/test_contextvars.py
similarity index 100%
rename from trio/_tests/test_contextvars.py
rename to src/trio/_tests/test_contextvars.py
diff --git a/trio/_tests/test_deprecate.py b/src/trio/_tests/test_deprecate.py
similarity index 100%
rename from trio/_tests/test_deprecate.py
rename to src/trio/_tests/test_deprecate.py
diff --git a/trio/_tests/test_dtls.py b/src/trio/_tests/test_dtls.py
similarity index 100%
rename from trio/_tests/test_dtls.py
rename to src/trio/_tests/test_dtls.py
diff --git a/trio/_tests/test_exports.py b/src/trio/_tests/test_exports.py
similarity index 100%
rename from trio/_tests/test_exports.py
rename to src/trio/_tests/test_exports.py
diff --git a/trio/_tests/test_fakenet.py b/src/trio/_tests/test_fakenet.py
similarity index 100%
rename from trio/_tests/test_fakenet.py
rename to src/trio/_tests/test_fakenet.py
diff --git a/trio/_tests/test_file_io.py b/src/trio/_tests/test_file_io.py
similarity index 100%
rename from trio/_tests/test_file_io.py
rename to src/trio/_tests/test_file_io.py
diff --git a/trio/_tests/test_highlevel_generic.py b/src/trio/_tests/test_highlevel_generic.py
similarity index 100%
rename from trio/_tests/test_highlevel_generic.py
rename to src/trio/_tests/test_highlevel_generic.py
diff --git a/trio/_tests/test_highlevel_open_tcp_listeners.py b/src/trio/_tests/test_highlevel_open_tcp_listeners.py
similarity index 100%
rename from trio/_tests/test_highlevel_open_tcp_listeners.py
rename to src/trio/_tests/test_highlevel_open_tcp_listeners.py
diff --git a/trio/_tests/test_highlevel_open_tcp_stream.py b/src/trio/_tests/test_highlevel_open_tcp_stream.py
similarity index 100%
rename from trio/_tests/test_highlevel_open_tcp_stream.py
rename to src/trio/_tests/test_highlevel_open_tcp_stream.py
diff --git a/trio/_tests/test_highlevel_open_unix_stream.py b/src/trio/_tests/test_highlevel_open_unix_stream.py
similarity index 100%
rename from trio/_tests/test_highlevel_open_unix_stream.py
rename to src/trio/_tests/test_highlevel_open_unix_stream.py
diff --git a/trio/_tests/test_highlevel_serve_listeners.py b/src/trio/_tests/test_highlevel_serve_listeners.py
similarity index 100%
rename from trio/_tests/test_highlevel_serve_listeners.py
rename to src/trio/_tests/test_highlevel_serve_listeners.py
diff --git a/trio/_tests/test_highlevel_socket.py b/src/trio/_tests/test_highlevel_socket.py
similarity index 100%
rename from trio/_tests/test_highlevel_socket.py
rename to src/trio/_tests/test_highlevel_socket.py
diff --git a/trio/_tests/test_highlevel_ssl_helpers.py b/src/trio/_tests/test_highlevel_ssl_helpers.py
similarity index 100%
rename from trio/_tests/test_highlevel_ssl_helpers.py
rename to src/trio/_tests/test_highlevel_ssl_helpers.py
diff --git a/trio/_tests/test_path.py b/src/trio/_tests/test_path.py
similarity index 100%
rename from trio/_tests/test_path.py
rename to src/trio/_tests/test_path.py
diff --git a/trio/_tests/test_scheduler_determinism.py b/src/trio/_tests/test_scheduler_determinism.py
similarity index 100%
rename from trio/_tests/test_scheduler_determinism.py
rename to src/trio/_tests/test_scheduler_determinism.py
diff --git a/trio/_tests/test_signals.py b/src/trio/_tests/test_signals.py
similarity index 100%
rename from trio/_tests/test_signals.py
rename to src/trio/_tests/test_signals.py
diff --git a/trio/_tests/test_socket.py b/src/trio/_tests/test_socket.py
similarity index 100%
rename from trio/_tests/test_socket.py
rename to src/trio/_tests/test_socket.py
diff --git a/trio/_tests/test_ssl.py b/src/trio/_tests/test_ssl.py
similarity index 100%
rename from trio/_tests/test_ssl.py
rename to src/trio/_tests/test_ssl.py
diff --git a/trio/_tests/test_subprocess.py b/src/trio/_tests/test_subprocess.py
similarity index 100%
rename from trio/_tests/test_subprocess.py
rename to src/trio/_tests/test_subprocess.py
diff --git a/trio/_tests/test_sync.py b/src/trio/_tests/test_sync.py
similarity index 100%
rename from trio/_tests/test_sync.py
rename to src/trio/_tests/test_sync.py
diff --git a/trio/_tests/test_testing.py b/src/trio/_tests/test_testing.py
similarity index 100%
rename from trio/_tests/test_testing.py
rename to src/trio/_tests/test_testing.py
diff --git a/trio/_tests/test_threads.py b/src/trio/_tests/test_threads.py
similarity index 100%
rename from trio/_tests/test_threads.py
rename to src/trio/_tests/test_threads.py
diff --git a/trio/_tests/test_timeouts.py b/src/trio/_tests/test_timeouts.py
similarity index 100%
rename from trio/_tests/test_timeouts.py
rename to src/trio/_tests/test_timeouts.py
diff --git a/trio/_tests/test_tracing.py b/src/trio/_tests/test_tracing.py
similarity index 100%
rename from trio/_tests/test_tracing.py
rename to src/trio/_tests/test_tracing.py
diff --git a/trio/_tests/test_unix_pipes.py b/src/trio/_tests/test_unix_pipes.py
similarity index 100%
rename from trio/_tests/test_unix_pipes.py
rename to src/trio/_tests/test_unix_pipes.py
diff --git a/trio/_tests/test_util.py b/src/trio/_tests/test_util.py
similarity index 100%
rename from trio/_tests/test_util.py
rename to src/trio/_tests/test_util.py
diff --git a/trio/_tests/test_wait_for_object.py b/src/trio/_tests/test_wait_for_object.py
similarity index 100%
rename from trio/_tests/test_wait_for_object.py
rename to src/trio/_tests/test_wait_for_object.py
diff --git a/trio/_tests/test_windows_pipes.py b/src/trio/_tests/test_windows_pipes.py
similarity index 100%
rename from trio/_tests/test_windows_pipes.py
rename to src/trio/_tests/test_windows_pipes.py
diff --git a/trio/_tests/tools/__init__.py b/src/trio/_tests/tools/__init__.py
similarity index 100%
rename from trio/_tests/tools/__init__.py
rename to src/trio/_tests/tools/__init__.py
diff --git a/trio/_tests/tools/test_gen_exports.py b/src/trio/_tests/tools/test_gen_exports.py
similarity index 100%
rename from trio/_tests/tools/test_gen_exports.py
rename to src/trio/_tests/tools/test_gen_exports.py
diff --git a/trio/_tests/tools/test_mypy_annotate.py b/src/trio/_tests/tools/test_mypy_annotate.py
similarity index 100%
rename from trio/_tests/tools/test_mypy_annotate.py
rename to src/trio/_tests/tools/test_mypy_annotate.py
diff --git a/trio/_tests/type_tests/check_wraps.py b/src/trio/_tests/type_tests/check_wraps.py
similarity index 100%
rename from trio/_tests/type_tests/check_wraps.py
rename to src/trio/_tests/type_tests/check_wraps.py
diff --git a/trio/_tests/type_tests/open_memory_channel.py b/src/trio/_tests/type_tests/open_memory_channel.py
similarity index 100%
rename from trio/_tests/type_tests/open_memory_channel.py
rename to src/trio/_tests/type_tests/open_memory_channel.py
diff --git a/trio/_tests/type_tests/path.py b/src/trio/_tests/type_tests/path.py
similarity index 100%
rename from trio/_tests/type_tests/path.py
rename to src/trio/_tests/type_tests/path.py
diff --git a/trio/_tests/verify_types_darwin.json b/src/trio/_tests/verify_types_darwin.json
similarity index 100%
rename from trio/_tests/verify_types_darwin.json
rename to src/trio/_tests/verify_types_darwin.json
diff --git a/trio/_tests/verify_types_linux.json b/src/trio/_tests/verify_types_linux.json
similarity index 100%
rename from trio/_tests/verify_types_linux.json
rename to src/trio/_tests/verify_types_linux.json
diff --git a/trio/_tests/verify_types_windows.json b/src/trio/_tests/verify_types_windows.json
similarity index 100%
rename from trio/_tests/verify_types_windows.json
rename to src/trio/_tests/verify_types_windows.json
diff --git a/trio/_threads.py b/src/trio/_threads.py
similarity index 100%
rename from trio/_threads.py
rename to src/trio/_threads.py
diff --git a/trio/_timeouts.py b/src/trio/_timeouts.py
similarity index 100%
rename from trio/_timeouts.py
rename to src/trio/_timeouts.py
diff --git a/trio/_tools/__init__.py b/src/trio/_tools/__init__.py
similarity index 100%
rename from trio/_tools/__init__.py
rename to src/trio/_tools/__init__.py
diff --git a/trio/_tools/gen_exports.py b/src/trio/_tools/gen_exports.py
similarity index 99%
rename from trio/_tools/gen_exports.py
rename to src/trio/_tools/gen_exports.py
index 8578b1e12d..3227a06018 100755
--- a/trio/_tools/gen_exports.py
+++ b/src/trio/_tools/gen_exports.py
@@ -313,7 +313,7 @@ def main() -> None:  # pragma: no cover
     source_root = Path.cwd()
     # Double-check we found the right directory
     assert (source_root / "LICENSE").exists()
-    core = source_root / "trio/_core"
+    core = source_root / "src/trio/_core"
     to_wrap = [
         File(core / "_run.py", "runner", imports=IMPORTS_RUN),
         File(
diff --git a/trio/_tools/mypy_annotate.py b/src/trio/_tools/mypy_annotate.py
similarity index 100%
rename from trio/_tools/mypy_annotate.py
rename to src/trio/_tools/mypy_annotate.py
diff --git a/trio/_unix_pipes.py b/src/trio/_unix_pipes.py
similarity index 100%
rename from trio/_unix_pipes.py
rename to src/trio/_unix_pipes.py
diff --git a/trio/_util.py b/src/trio/_util.py
similarity index 100%
rename from trio/_util.py
rename to src/trio/_util.py
diff --git a/trio/_version.py b/src/trio/_version.py
similarity index 100%
rename from trio/_version.py
rename to src/trio/_version.py
diff --git a/trio/_wait_for_object.py b/src/trio/_wait_for_object.py
similarity index 100%
rename from trio/_wait_for_object.py
rename to src/trio/_wait_for_object.py
diff --git a/trio/_windows_pipes.py b/src/trio/_windows_pipes.py
similarity index 100%
rename from trio/_windows_pipes.py
rename to src/trio/_windows_pipes.py
diff --git a/trio/abc.py b/src/trio/abc.py
similarity index 100%
rename from trio/abc.py
rename to src/trio/abc.py
diff --git a/trio/from_thread.py b/src/trio/from_thread.py
similarity index 100%
rename from trio/from_thread.py
rename to src/trio/from_thread.py
diff --git a/trio/lowlevel.py b/src/trio/lowlevel.py
similarity index 100%
rename from trio/lowlevel.py
rename to src/trio/lowlevel.py
diff --git a/trio/py.typed b/src/trio/py.typed
similarity index 100%
rename from trio/py.typed
rename to src/trio/py.typed
diff --git a/trio/socket.py b/src/trio/socket.py
similarity index 100%
rename from trio/socket.py
rename to src/trio/socket.py
diff --git a/trio/testing/__init__.py b/src/trio/testing/__init__.py
similarity index 100%
rename from trio/testing/__init__.py
rename to src/trio/testing/__init__.py
diff --git a/trio/testing/_check_streams.py b/src/trio/testing/_check_streams.py
similarity index 100%
rename from trio/testing/_check_streams.py
rename to src/trio/testing/_check_streams.py
diff --git a/trio/testing/_checkpoints.py b/src/trio/testing/_checkpoints.py
similarity index 100%
rename from trio/testing/_checkpoints.py
rename to src/trio/testing/_checkpoints.py
diff --git a/trio/testing/_fake_net.py b/src/trio/testing/_fake_net.py
similarity index 100%
rename from trio/testing/_fake_net.py
rename to src/trio/testing/_fake_net.py
diff --git a/trio/testing/_memory_streams.py b/src/trio/testing/_memory_streams.py
similarity index 100%
rename from trio/testing/_memory_streams.py
rename to src/trio/testing/_memory_streams.py
diff --git a/trio/testing/_network.py b/src/trio/testing/_network.py
similarity index 100%
rename from trio/testing/_network.py
rename to src/trio/testing/_network.py
diff --git a/trio/testing/_sequencer.py b/src/trio/testing/_sequencer.py
similarity index 100%
rename from trio/testing/_sequencer.py
rename to src/trio/testing/_sequencer.py
diff --git a/trio/testing/_trio_test.py b/src/trio/testing/_trio_test.py
similarity index 100%
rename from trio/testing/_trio_test.py
rename to src/trio/testing/_trio_test.py
diff --git a/trio/tests.py b/src/trio/tests.py
similarity index 100%
rename from trio/tests.py
rename to src/trio/tests.py
diff --git a/trio/to_thread.py b/src/trio/to_thread.py
similarity index 100%
rename from trio/to_thread.py
rename to src/trio/to_thread.py