diff --git a/lib/std/c.zig b/lib/std/c.zig
index 6a8e142a0ce5bc07f92cc04cf4d5ae5d6a76762d..56dbe04ba515345f7738db99ca1f0dd4c2a8fc90 100644
--- a/lib/std/c.zig
+++ b/lib/std/c.zig
@@ -10810,6 +10810,16 @@ pub const ptrace = switch (native_os) {
     else => {},
 };
 
+pub extern "c" fn semget(key: std.posix.key_t, nsems: c_int, semflg: c_int) c_int;
+pub extern "c" fn semctl(semid: c_int, semnum: c_int, op: c_int, ...) c_int;
+pub extern "c" fn semop(semid: c_int, sops: [*]std.posix.sembuf, nsops: usize) c_int;
+pub extern "c" fn semtimedop(
+    semid: c_int,
+    sops: [*]std.posix.sembuf,
+    nsops: usize,
+    timeout: ?*const timespec,
+) c_int;
+
 pub extern "c" fn sem_init(sem: *sem_t, pshared: c_int, value: c_uint) c_int;
 pub extern "c" fn sem_destroy(sem: *sem_t) c_int;
 pub extern "c" fn sem_open(name: [*:0]const u8, flag: c_int, mode: mode_t, value: c_uint) *sem_t;
diff --git a/lib/std/posix.zig b/lib/std/posix.zig
index aeed9e5d8e4816c24da7a0cb9c767344f7b9c414..879f4229374f196f3263d4024e4cf4183ebe6356 100644
--- a/lib/std/posix.zig
+++ b/lib/std/posix.zig
@@ -275,6 +275,99 @@ pub const LOG = struct {
     pub const DEBUG = 7;
 };
 
+pub const key_t = switch (native_os) {
+    .linux, .illumos => enum(c_int) {
+        IPC_PRIVATE = 0,
+        _,
+    },
+    .freebsd, .netbsd, .openbsd, .dragonfly => enum(c_long) {
+        IPC_PRIVATE = 0,
+        _,
+    },
+    .haiku,
+    .driverkit,
+    .ios,
+    .maccatalyst,
+    .macos,
+    .tvos,
+    .visionos,
+    .watchos,
+    => enum(i32) {
+        IPC_PRIVATE = 0,
+        _,
+    },
+    else => unreachable,
+};
+pub const SETVAL = switch (native_os) {
+    .linux => 16,
+
+    .illumos,
+    .haiku,
+
+    .freebsd,
+    .netbsd,
+    .openbsd,
+    .dragonfly,
+
+    .driverkit,
+    .ios,
+    .maccatalyst,
+    .macos,
+    .tvos,
+    .visionos,
+    .watchos,
+    => 8,
+
+    else => unreachable,
+};
+pub const SEM_UNDO = switch (native_os) {
+    .linux,
+    .illumos,
+
+    .freebsd,
+    .netbsd,
+    .openbsd,
+    .dragonfly,
+
+    .driverkit,
+    .ios,
+    .maccatalyst,
+    .macos,
+    .tvos,
+    .visionos,
+    .watchos,
+    => 0x1000,
+
+    .haiku => 10,
+
+    else => unreachable,
+};
+pub const sembuf = switch (native_os) {
+    .linux,
+    .illumos,
+    .haiku,
+
+    .freebsd,
+    .netbsd,
+    .openbsd,
+    .dragonfly,
+
+    .driverkit,
+    .ios,
+    .maccatalyst,
+    .macos,
+    .tvos,
+    .visionos,
+    .watchos,
+    => extern struct {
+        sem_num: c_ushort,
+        sem_op: c_short,
+        sem_flg: c_short,
+    },
+
+    else => unreachable,
+};
+
 pub const socket_t = if (native_os == .windows) windows.ws2_32.SOCKET else fd_t;
 
 /// Obtains errno from the return value of a system function call.