diff --git a/build.rs b/build.rs
index cde1b35294deb..165f0bef561e3 100644
--- a/build.rs
+++ b/build.rs
@@ -23,7 +23,10 @@ const ALLOWED_CFGS: &'static [&'static str] = &[
 
 // Extra values to allow for check-cfg.
 const CHECK_CFG_EXTRA: &'static [(&'static str, &'static [&'static str])] = &[
-    ("target_os", &["switch", "aix", "ohos", "hurd", "visionos"]),
+    (
+        "target_os",
+        &["switch", "aix", "ohos", "hurd", "rtems", "visionos"],
+    ),
     ("target_env", &["illumos", "wasi", "aix", "ohos"]),
     (
         "target_arch",
diff --git a/src/unix/newlib/mod.rs b/src/unix/newlib/mod.rs
index 45a2668aac71a..4fbac95661818 100644
--- a/src/unix/newlib/mod.rs
+++ b/src/unix/newlib/mod.rs
@@ -258,6 +258,16 @@ cfg_if! {
         pub const __SIZEOF_PTHREAD_RWLOCK_T: usize = 4;
         pub const __SIZEOF_PTHREAD_RWLOCKATTR_T: usize = 4;
         pub const __SIZEOF_PTHREAD_BARRIER_T: usize = 4;
+    } else if #[cfg(target_os = "rtems")] {
+        const __PTHREAD_INITIALIZER_BYTE: u8 = 0x00;
+        pub const __SIZEOF_PTHREAD_ATTR_T: usize = 96;
+        pub const __SIZEOF_PTHREAD_MUTEX_T: usize = 64;
+        pub const __SIZEOF_PTHREAD_MUTEXATTR_T: usize = 24;
+        pub const __SIZEOF_PTHREAD_COND_T: usize = 28;
+        pub const __SIZEOF_PTHREAD_CONDATTR_T: usize = 24;
+        pub const __SIZEOF_PTHREAD_RWLOCK_T: usize = 32;
+        pub const __SIZEOF_PTHREAD_RWLOCKATTR_T: usize = 8;
+        pub const __SIZEOF_PTHREAD_BARRIER_T: usize = 32;
     } else {
         const __PTHREAD_INITIALIZER_BYTE: u8 = 0;
         pub const __SIZEOF_PTHREAD_ATTR_T: usize = 56;
@@ -767,6 +777,13 @@ cfg_if! {
     }
 }
 
+cfg_if! {
+    if #[cfg(target_os = "rtems")] {
+        mod rtems;
+        pub use self::rtems::*;
+    }
+}
+
 #[macro_use]
 mod align;
 expand_align!();
diff --git a/src/unix/newlib/rtems/mod.rs b/src/unix/newlib/rtems/mod.rs
new file mode 100644
index 0000000000000..36f4820c92f4f
--- /dev/null
+++ b/src/unix/newlib/rtems/mod.rs
@@ -0,0 +1,141 @@
+// defined in architecture specific module
+use c_long;
+
+s! {
+    pub struct sockaddr_un {
+        pub sun_family: ::sa_family_t,
+        pub sun_path: [::c_char; 108usize],
+    }
+}
+
+pub const AF_UNIX: ::c_int = 1;
+
+pub const RTLD_DEFAULT: *mut ::c_void = -2isize as *mut ::c_void;
+
+pub const UTIME_OMIT: c_long = -1;
+pub const AT_FDCWD: ::c_int = -2;
+
+pub const O_DIRECTORY: ::c_int = 0x200000;
+pub const O_NOFOLLOW: ::c_int = 0x100000;
+
+pub const AT_EACCESS: ::c_int = 1;
+pub const AT_SYMLINK_NOFOLLOW: ::c_int = 2;
+pub const AT_SYMLINK_FOLLOW: ::c_int = 4;
+pub const AT_REMOVEDIR: ::c_int = 8;
+
+// signal.h
+pub const SIG_BLOCK: ::c_int = 1;
+pub const SIG_UNBLOCK: ::c_int = 2;
+pub const SIG_SETMASK: ::c_int = 0;
+pub const SIGHUP: ::c_int = 1;
+pub const SIGINT: ::c_int = 2;
+pub const SIGQUIT: ::c_int = 3;
+pub const SIGILL: ::c_int = 4;
+pub const SIGTRAP: ::c_int = 5;
+pub const SIGABRT: ::c_int = 6;
+pub const SIGEMT: ::c_int = 7;
+pub const SIGFPE: ::c_int = 8;
+pub const SIGKILL: ::c_int = 9;
+pub const SIGBUS: ::c_int = 10;
+pub const SIGSEGV: ::c_int = 11;
+pub const SIGSYS: ::c_int = 12;
+pub const SIGPIPE: ::c_int = 13;
+pub const SIGALRM: ::c_int = 14;
+pub const SIGTERM: ::c_int = 15;
+pub const SIGURG: ::c_int = 16;
+pub const SIGSTOP: ::c_int = 17;
+pub const SIGTSTP: ::c_int = 18;
+pub const SIGCONT: ::c_int = 19;
+pub const SIGCHLD: ::c_int = 20;
+pub const SIGCLD: ::c_int = 20;
+pub const SIGTTIN: ::c_int = 21;
+pub const SIGTTOU: ::c_int = 22;
+pub const SIGIO: ::c_int = 23;
+pub const SIGWINCH: ::c_int = 24;
+pub const SIGUSR1: ::c_int = 25;
+pub const SIGUSR2: ::c_int = 26;
+pub const SIGRTMIN: ::c_int = 27;
+pub const SIGRTMAX: ::c_int = 31;
+pub const SIGXCPU: ::c_int = 24;
+pub const SIGXFSZ: ::c_int = 25;
+pub const SIGVTALRM: ::c_int = 26;
+pub const SIGPROF: ::c_int = 27;
+
+pub const SA_NOCLDSTOP: ::c_ulong = 0x00000001;
+pub const SA_SIGINFO: ::c_ulong = 0x00000002;
+pub const SA_ONSTACK: ::c_ulong = 0x00000004;
+
+pub const EAI_AGAIN: ::c_int = 2;
+pub const EAI_BADFLAGS: ::c_int = 3;
+pub const EAI_FAIL: ::c_int = 4;
+pub const EAI_SERVICE: ::c_int = 9;
+pub const EAI_SYSTEM: ::c_int = 11;
+pub const EAI_OVERFLOW: ::c_int = 14;
+
+pub const _SC_PAGESIZE: ::c_int = 8;
+pub const _SC_GETPW_R_SIZE_MAX: ::c_int = 51;
+pub const PTHREAD_STACK_MIN: ::size_t = 0;
+
+// sys/wait.h
+pub const WNOHANG: ::c_int = 1;
+pub const WUNTRACED: ::c_int = 2;
+
+// sys/socket.h
+pub const SOMAXCONN: ::c_int = 128;
+
+safe_f! {
+    pub {const} fn WIFSTOPPED(status: ::c_int) -> bool {
+        (status & 0xff) == 0x7f
+    }
+
+    pub {const} fn WSTOPSIG(status: ::c_int) -> ::c_int {
+        // (status >> 8) & 0xff
+        WEXITSTATUS(status)
+    }
+
+    pub {const} fn WIFSIGNALED(status: ::c_int) -> bool {
+        ((status & 0x7f) > 0) && ((status & 0x7f) < 0x7f)
+    }
+
+    pub {const} fn WTERMSIG(status: ::c_int) -> ::c_int {
+        status & 0x7f
+    }
+
+    pub {const} fn WIFEXITED(status: ::c_int) -> bool {
+        (status & 0xff) == 0
+    }
+
+    pub {const} fn WEXITSTATUS(status: ::c_int) -> ::c_int {
+        (status >> 8) & 0xff
+    }
+
+    // RTEMS doesn't have native WIFCONTINUED.
+    pub {const} fn WIFCONTINUED(_status: ::c_int) -> bool {
+        true
+    }
+
+    // RTEMS doesn't have native WCOREDUMP.
+    pub {const} fn WCOREDUMP(_status: ::c_int) -> bool {
+        false
+    }
+}
+
+extern "C" {
+    pub fn futimens(fd: ::c_int, times: *const ::timespec) -> ::c_int;
+    pub fn writev(fd: ::c_int, iov: *const ::iovec, iovcnt: ::c_int) -> ::ssize_t;
+    pub fn readv(fd: ::c_int, iov: *const ::iovec, iovcnt: ::c_int) -> ::ssize_t;
+
+    pub fn pthread_create(
+        native: *mut ::pthread_t,
+        attr: *const ::pthread_attr_t,
+        f: extern "C" fn(_: *mut ::c_void) -> *mut ::c_void,
+        value: *mut ::c_void,
+    ) -> ::c_int;
+
+    pub fn pthread_condattr_setclock(
+        attr: *mut ::pthread_condattr_t,
+        clock_id: ::clockid_t,
+    ) -> ::c_int;
+
+    pub fn setgroups(ngroups: ::c_int, grouplist: *const ::gid_t) -> ::c_int;
+}