diff --git a/lib/std/c.zig b/lib/std/c.zig
index c1523cd68a54..0ee7f32e5c3d 100644
--- a/lib/std/c.zig
+++ b/lib/std/c.zig
@@ -2753,6 +2753,19 @@ pub const Sigaction = switch (native_os) {
             restorer: ?*const fn () callconv(.C) void = null,
             __resv: [1]c_int = .{0},
         },
+        .s390x => if (builtin.abi == .gnu) extern struct {
+            pub const handler_fn = *align(1) const fn (i32) callconv(.C) void;
+            pub const sigaction_fn = *const fn (i32, *const siginfo_t, ?*anyopaque) callconv(.C) void;
+
+            handler: extern union {
+                handler: ?handler_fn,
+                sigaction: ?sigaction_fn,
+            },
+            __glibc_reserved0: c_int = 0,
+            flags: c_uint,
+            restorer: ?*const fn () callconv(.C) void = null,
+            mask: sigset_t,
+        } else linux.Sigaction,
         else => linux.Sigaction,
     },
     .emscripten => emscripten.Sigaction,
diff --git a/lib/std/debug.zig b/lib/std/debug.zig
index 0cb201373a73..ad43caee5922 100644
--- a/lib/std/debug.zig
+++ b/lib/std/debug.zig
@@ -61,6 +61,7 @@ pub const sys_can_stack_trace = switch (builtin.cpu.arch) {
     .mipsel,
     .mips64,
     .mips64el,
+    .s390x,
     => false,
 
     // `@returnAddress()` in LLVM 10 gives
diff --git a/lib/std/os/linux.zig b/lib/std/os/linux.zig
index aaf08395fa48..40dfcb933b57 100644
--- a/lib/std/os/linux.zig
+++ b/lib/std/os/linux.zig
@@ -904,7 +904,19 @@ pub fn mmap(address: ?[*]u8, length: usize, prot: usize, flags: MAP, fd: i32, of
             @truncate(@as(u64, @bitCast(offset)) / MMAP2_UNIT),
         );
     } else {
-        return syscall6(
+        // The s390x mmap() syscall existed before Linux supported syscalls with 5+ parameters, so
+        // it takes a single pointer to an array of arguments instead.
+        return if (native_arch == .s390x) syscall1(
+            .mmap,
+            @intFromPtr(&[_]usize{
+                @intFromPtr(address),
+                length,
+                prot,
+                @as(u32, @bitCast(flags)),
+                @bitCast(@as(isize, fd)),
+                @as(u64, @bitCast(offset)),
+            }),
+        ) else syscall6(
             .mmap,
             @intFromPtr(address),
             length,
diff --git a/lib/std/os/linux/tls.zig b/lib/std/os/linux/tls.zig
index 7dab38024ca6..d1292e86dd03 100644
--- a/lib/std/os/linux/tls.zig
+++ b/lib/std/os/linux/tls.zig
@@ -541,7 +541,19 @@ inline fn mmap(address: ?[*]u8, length: usize, prot: usize, flags: linux.MAP, fd
             @as(usize, @truncate(@as(u64, @bitCast(offset)) / linux.MMAP2_UNIT)),
         });
     } else {
-        return @call(.always_inline, linux.syscall6, .{
+        // The s390x mmap() syscall existed before Linux supported syscalls with 5+ parameters, so
+        // it takes a single pointer to an array of arguments instead.
+        return if (native_arch == .s390x) @call(.always_inline, linux.syscall1, .{
+            .mmap,
+            @intFromPtr(&[_]usize{
+                @intFromPtr(address),
+                length,
+                prot,
+                @as(u32, @bitCast(flags)),
+                @as(usize, @bitCast(@as(isize, fd))),
+                @as(u64, @bitCast(offset)),
+            }),
+        }) else @call(.always_inline, linux.syscall6, .{
             .mmap,
             @intFromPtr(address),
             length,
diff --git a/lib/std/posix/test.zig b/lib/std/posix/test.zig
index e62ffa39ca54..dba7dcde6d9c 100644
--- a/lib/std/posix/test.zig
+++ b/lib/std/posix/test.zig
@@ -368,6 +368,11 @@ test "fstatat" {
     // now repeat but using `fstatat` instead
     const flags = if (native_os == .wasi) 0x0 else posix.AT.SYMLINK_NOFOLLOW;
     const statat = try posix.fstatat(tmp.dir.fd, "file.txt", flags);
+
+    // s390x-linux does not have nanosecond precision for fstat(), but it does for fstatat(). As a
+    // result, comparing the two structures is doomed to fail.
+    if (builtin.cpu.arch == .s390x and builtin.os.tag == .linux) return error.SkipZigTest;
+
     try expectEqual(stat, statat);
 }
 
diff --git a/src/codegen/llvm.zig b/src/codegen/llvm.zig
index 2cd1af783e23..1f21516e9ea8 100644
--- a/src/codegen/llvm.zig
+++ b/src/codegen/llvm.zig
@@ -12241,6 +12241,7 @@ fn ccAbiPromoteInt(
             .sparc64,
             .powerpc64,
             .powerpc64le,
+            .s390x,
             => switch (int_info.bits) {
                 0...63 => int_info.signedness,
                 else => null,
diff --git a/test/tests.zig b/test/tests.zig
index 1d6c33bd2448..1e98a48489a4 100644
--- a/test/tests.zig
+++ b/test/tests.zig
@@ -636,6 +636,30 @@ const test_targets = blk: {
             .use_lld = false,
         },
 
+        .{
+            .target = .{
+                .cpu_arch = .s390x,
+                .os_tag = .linux,
+                .abi = .none,
+            },
+        },
+        .{
+            .target = .{
+                .cpu_arch = .s390x,
+                .os_tag = .linux,
+                .abi = .musl,
+            },
+            .link_libc = true,
+        },
+        .{
+            .target = .{
+                .cpu_arch = .s390x,
+                .os_tag = .linux,
+                .abi = .gnu,
+            },
+            .link_libc = true,
+        },
+
         .{
             .target = .{
                 .cpu_arch = .x86_64,