diff --git a/trio/_subprocess/__init__.py b/trio/_subprocess/__init__.py
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/trio/_subprocess/unix_pipes.py b/trio/_subprocess/unix_pipes.py
new file mode 100644
index 0000000000..f62fa8f590
--- /dev/null
+++ b/trio/_subprocess/unix_pipes.py
@@ -0,0 +1,120 @@
+import fcntl
+import os
+from typing import Tuple
+
+from .. import _core, BrokenStreamError
+from .._abc import SendStream, ReceiveStream
+
+__all__ = ["PipeSendStream", "PipeReceiveStream", "make_pipe"]
+
+
+class _PipeMixin:
+    def __init__(self, pipefd: int):
+        if not isinstance(pipefd, int):
+            raise TypeError(
+                "{0.__class__.__name__} needs a pipe fd".format(self)
+            )
+
+        self._pipe = pipefd
+        self._closed = False
+
+        flags = fcntl.fcntl(self._pipe, fcntl.F_GETFL)
+        fcntl.fcntl(self._pipe, fcntl.F_SETFL, flags | os.O_NONBLOCK)
+
+    def _close(self):
+        if self._closed:
+            return
+
+        self._closed = True
+        os.close(self._pipe)
+
+    async def aclose(self):
+        # XX: This would be in _close, but this can only be used from an
+        # async context.
+        _core.notify_fd_close(self._pipe)
+        self._close()
+        await _core.checkpoint()
+
+    def fileno(self) -> int:
+        """Gets the file descriptor for this pipe."""
+        return self._pipe
+
+    def __del__(self):
+        self._close()
+
+
+class PipeSendStream(_PipeMixin, SendStream):
+    """Represents a send stream over an os.pipe object."""
+
+    async def send_all(self, data: bytes):
+        # we have to do this no matter what
+        await _core.checkpoint()
+        if self._closed:
+            raise _core.ClosedResourceError("this pipe is already closed")
+
+        if not data:
+            return
+
+        length = len(data)
+        # adapted from the SocketStream code
+        with memoryview(data) as view:
+            total_sent = 0
+            while total_sent < length:
+                with view[total_sent:] as remaining:
+                    try:
+                        total_sent += os.write(self._pipe, remaining)
+                    except BrokenPipeError as e:
+                        await _core.checkpoint()
+                        raise BrokenStreamError from e
+                    except BlockingIOError:
+                        await self.wait_send_all_might_not_block()
+
+    async def wait_send_all_might_not_block(self) -> None:
+        if self._closed:
+            await _core.checkpoint()
+            raise _core.ClosedResourceError("This pipe is already closed")
+
+        try:
+            await _core.wait_writable(self._pipe)
+        except BrokenPipeError as e:
+            # kqueue: raises EPIPE on wait_writable instead
+            # of sending, which is annoying
+            # also doesn't checkpoint so we have to do that
+            # ourselves here too
+            await _core.checkpoint()
+            raise BrokenStreamError from e
+
+
+class PipeReceiveStream(_PipeMixin, ReceiveStream):
+    """Represents a receive stream over an os.pipe object."""
+
+    async def receive_some(self, max_bytes: int) -> bytes:
+        if self._closed:
+            await _core.checkpoint()
+            raise _core.ClosedResourceError("this pipe is already closed")
+
+        if not isinstance(max_bytes, int):
+            await _core.checkpoint()
+            raise TypeError("max_bytes must be integer >= 1")
+
+        if max_bytes < 1:
+            await _core.checkpoint()
+            raise ValueError("max_bytes must be integer >= 1")
+
+        while True:
+            try:
+                await _core.checkpoint_if_cancelled()
+                data = os.read(self._pipe, max_bytes)
+            except BlockingIOError:
+                await _core.wait_readable(self._pipe)
+            else:
+                await _core.cancel_shielded_checkpoint()
+                break
+
+        return data
+
+
+async def make_pipe() -> Tuple[PipeSendStream, PipeReceiveStream]:
+    """Makes a new pair of pipes."""
+    (r, w) = os.pipe()
+    return PipeSendStream(w), PipeReceiveStream(r)
diff --git a/trio/tests/subprocess/__init__.py b/trio/tests/subprocess/__init__.py
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/trio/tests/subprocess/test_unix_pipes.py b/trio/tests/subprocess/test_unix_pipes.py
new file mode 100644
index 0000000000..b8cc2d496a
--- /dev/null
+++ b/trio/tests/subprocess/test_unix_pipes.py
@@ -0,0 +1,148 @@
+import errno
+import select
+
+import os
+import pytest
+
+from trio._core.tests.tutil import gc_collect_harder
+from ... import _core
+from ...testing import (wait_all_tasks_blocked, check_one_way_stream)
+
+posix = os.name == "posix"
+
+pytestmark = pytest.mark.skipif(
+    not posix, reason="pipes are only supported on posix"
+)
+
+if posix:
+    from ..._subprocess.unix_pipes import (
+        PipeSendStream, PipeReceiveStream, make_pipe
+    )
+
+
+async def test_send_pipe():
+    r, w = os.pipe()
+    send = PipeSendStream(w)
+    assert send.fileno() == w
+    await send.send_all(b"123")
+    assert (os.read(r, 8)) == b"123"
+
+    os.close(r)
+    os.close(w)
+    send._closed = True
+
+
+async def test_receive_pipe():
+    r, w = os.pipe()
+    recv = PipeReceiveStream(r)
+    assert (recv.fileno()) == r
+    os.write(w, b"123")
+    assert (await recv.receive_some(8)) == b"123"
+
+    os.close(r)
+    os.close(w)
+    recv._closed = True
+
+
+async def test_pipes_combined():
+    write, read = await make_pipe()
+    count = 2**20
+
+    async def sender():
+        big = bytearray(count)
+        await write.send_all(big)
+
+    async def reader():
+        await wait_all_tasks_blocked()
+        received = 0
+        while received < count:
+            received += len(await read.receive_some(4096))
+
+        assert received == count
+
+    async with _core.open_nursery() as n:
+        n.start_soon(sender)
+        n.start_soon(reader)
+
+    await read.aclose()
+    await write.aclose()
+
+
+async def test_send_on_closed_pipe():
+    write, read = await make_pipe()
+    await write.aclose()
+
+    with pytest.raises(_core.ClosedResourceError):
+        await write.send_all(b"123")
+
+    await read.aclose()
+
+
+async def test_pipe_errors():
+    with pytest.raises(TypeError):
+        PipeReceiveStream(None)
+
+    with pytest.raises(ValueError):
+        await PipeReceiveStream(0).receive_some(0)
+
+
+async def test_del():
+    w, r = await make_pipe()
+    f1, f2 = w.fileno(), r.fileno()
+    del w, r
+    gc_collect_harder()
+
+    with pytest.raises(OSError) as excinfo:
+        os.close(f1)
+    assert excinfo.value.errno == errno.EBADF
+
+    with pytest.raises(OSError) as excinfo:
+        os.close(f2)
+    assert excinfo.value.errno == errno.EBADF
+
+
+async def test_async_with():
+    w, r = await make_pipe()
+    async with w, r:
+        pass
+
+    assert w._closed
+    assert r._closed
+
+    with pytest.raises(OSError) as excinfo:
+        os.close(w.fileno())
+    assert excinfo.value.errno == errno.EBADF
+
+    with pytest.raises(OSError) as excinfo:
+        os.close(r.fileno())
+    assert excinfo.value.errno == errno.EBADF
+
+
+async def make_clogged_pipe():
+    s, r = await make_pipe()
+    try:
+        while True:
+            # We want to totally fill up the pipe buffer.
+            # This requires working around a weird feature that POSIX pipes
+            # have.
+            # If you do a write of <= PIPE_BUF bytes, then it's guaranteed
+            # to either complete entirely, or not at all. So if we tried to
+            # write PIPE_BUF bytes, and the buffer's free space is only
+            # PIPE_BUF/2, then the write will raise BlockingIOError... even
+            # though a smaller write could still succeed! To avoid this,
+            # make sure to write >PIPE_BUF bytes each time, which disables
+            # the special behavior.
+            # For details, search for PIPE_BUF here:
+            #   http://pubs.opengroup.org/onlinepubs/9699919799/functions/write.html
+
+            # for the getattr:
+            # https://bitbucket.org/pypy/pypy/issues/2876/selectpipe_buf-is-missing-on-pypy3
+            buf_size = getattr(select, "PIPE_BUF", 8192)
+            os.write(s.fileno(), b"x" * buf_size * 2)
+    except BlockingIOError:
+        pass
+    return s, r
+
+
+async def test_pipe_fully():
+    await check_one_way_stream(make_pipe, make_clogged_pipe)