diff --git a/CHANGELOG.md b/CHANGELOG.md
index 71f9c7ce8..aa515444c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,13 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [Unreleased]
+
+### Added
+- `RawOsError` type alias [#739]
+
+[#739]: https://github.com/rust-random/getrandom/pull/739
+
 ## [0.3.4] - 2025-10-14
 
 ### Major change to `wasm_js` backend
@@ -631,6 +638,7 @@ Publish initial implementation.
 ## [0.0.0] - 2019-01-19
 Publish an empty template library.
 
+[Unreleased]: https://github.com/rust-random/getrandom/compare/v0.3.4...master
 [0.3.4]: https://github.com/rust-random/getrandom/compare/v0.3.3...v0.3.4
 [0.3.3]: https://github.com/rust-random/getrandom/compare/v0.3.2...v0.3.3
 [0.3.2]: https://github.com/rust-random/getrandom/compare/v0.3.1...v0.3.2
diff --git a/src/error.rs b/src/error.rs
index 284533d10..99a29aa3d 100644
--- a/src/error.rs
+++ b/src/error.rs
@@ -3,17 +3,26 @@ extern crate std;
 
 use core::fmt;
 
-// This private alias mirrors `std::io::RawOsError`:
-// https://doc.rust-lang.org/std/io/type.RawOsError.html)
 cfg_if::cfg_if!(
     if #[cfg(target_os = "uefi")] {
         // See the UEFI spec for more information:
         // https://uefi.org/specs/UEFI/2.10/Apx_D_Status_Codes.html
-        type RawOsError = usize;
+
+        /// Raw error code.
+        ///
+        /// This alias mirrors unstable [`std::io::RawOsError`].
+        ///
+        /// [`std::io::RawOsError`]: https://doc.rust-lang.org/std/io/type.RawOsError.html
+        pub type RawOsError = usize;
         type NonZeroRawOsError = core::num::NonZeroUsize;
         const UEFI_ERROR_FLAG: RawOsError = 1 << (RawOsError::BITS - 1);
     } else {
-        type RawOsError = i32;
+        /// Raw error code.
+        ///
+        /// This alias mirrors unstable [`std::io::RawOsError`].
+        ///
+        /// [`std::io::RawOsError`]: https://doc.rust-lang.org/std/io/type.RawOsError.html
+        pub type RawOsError = i32;
         type NonZeroRawOsError = core::num::NonZeroI32;
     }
 );
diff --git a/src/lib.rs b/src/lib.rs
index adb7e5b7e..c98ea19dc 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -39,7 +39,7 @@ mod util;
 #[cfg(feature = "std")]
 mod error_std_impls;
 
-pub use crate::error::Error;
+pub use crate::error::{Error, RawOsError};
 
 /// Fill `dest` with random bytes from the system's preferred random number source.
 ///