diff --git a/doc/known-issues.md b/doc/known-issues.md
index 5969bd0b..2f93a2dc 100644
--- a/doc/known-issues.md
+++ b/doc/known-issues.md
@@ -44,3 +44,15 @@ This is [a bug in Dawn](https://github.com/NixOS/nixpkgs/issues/150398), you can
 ```
 LD_PRELOAD=/run/current-system/profile/lib/libvulkan.so zig-out/bin/gpu-hello-triangle
 ```
+
+## Choosing a different GitHub download mirror (Chinese users)
+
+**Background**: `zig build` on the first time around will download a 20-30MB file of Dawn (Google's WebGPU implementation) from https://github.com/hexops/mach-gpu-dawn/releases - the build system uses `curl` to do this automatically. You can of course build Dawn from source using the `-Ddawn-from-source=true` flag, but this will require a clone of the Dawn sources which are a larger download and takes a few minutes to build as it is a large C++ codebase.
+
+Users in Chinese mainland may find that download speeds to github.com are too slow (hours to download a 30 MB file), and apparently it is common to use GitHub mirror sites like https://fastgit.org to download files from GitHub.
+
+You can have Mach use such websites by setting an environment variable e.g.:
+
+```sh
+MACH_GITHUB_BASE_URL=https://download.fastgit.org
+```
diff --git a/libs/gpu-dawn/sdk.zig b/libs/gpu-dawn/sdk.zig
index bc3f4206..6af604b9 100644
--- a/libs/gpu-dawn/sdk.zig
+++ b/libs/gpu-dawn/sdk.zig
@@ -169,6 +169,15 @@ pub fn Sdk(comptime deps: anytype) type {
             }
         }
 
+        fn getGitHubBaseURLOwned(allocator: std.mem.Allocator) []const u8 {
+            if (std.process.getEnvVarOwned(allocator, "MACH_GITHUB_BASE_URL")) |base_url| {
+                std.log.info("mach: respecting MACH_GITHUB_BASE_URL: {s}\n", .{base_url});
+                return base_url;
+            } else |_| {
+                return "https://github.com";
+            }
+        }
+
         pub fn linkFromBinary(b: *Builder, step: *std.build.LibExeObjStep, options: Options) void {
             const target = step.target_info.target;
             const binaries_available = switch (target.os.tag) {
@@ -321,11 +330,14 @@ pub fn Sdk(comptime deps: anytype) type {
 
             // Compose the download URL, e.g.:
             // https://github.com/hexops/mach-gpu-dawn/releases/download/release-6b59025/libdawn_x86_64-macos-none_debug.a.gz
+            const github_base_url = getGitHubBaseURLOwned(allocator);
+            defer allocator.free(github_base_url);
             const lib_prefix = if (is_windows) "dawn_" else "libdawn_";
             const lib_ext = if (is_windows) ".lib" else ".a";
             const lib_file_name = if (is_windows) "dawn.lib" else "libdawn.a";
             const download_url = try std.mem.concat(allocator, u8, &.{
-                "https://github.com/hexops/mach-gpu-dawn/releases/download/",
+                github_base_url,
+                "/hexops/mach-gpu-dawn/releases/download/",
                 version,
                 "/",
                 lib_prefix,