diff --git a/platforms/BUILD.bazel b/platforms/BUILD.bazel
index d9c7140dc..3d78b56a8 100644
--- a/platforms/BUILD.bazel
+++ b/platforms/BUILD.bazel
@@ -45,3 +45,11 @@ platform(
         "@platforms//cpu:aarch64",
     ],
 )
+
+platform(
+    name = "windows-x86_64",
+    constraint_values = [
+        "@platforms//os:windows",
+        "@platforms//cpu:x86_64",
+    ],
+)
diff --git a/toolchain/BUILD.llvm_repo_windows b/toolchain/BUILD.llvm_repo_windows
new file mode 100644
index 000000000..baca19e4f
--- /dev/null
+++ b/toolchain/BUILD.llvm_repo_windows
@@ -0,0 +1,170 @@
+# Copyright 2021 The Bazel Authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+package(default_visibility = ["//visibility:public"])
+
+# Some targets may need to directly depend on these files.
+exports_files(glob([
+    "bin/*",
+    "lib/*",
+    "include/*",
+]))
+
+## LLVM toolchain files
+
+ALL_DLLS = glob(["bin/*.dll"])
+
+filegroup(
+    name = "clang",
+    srcs = [
+        "bin/clang.exe",
+        "bin/clang++.exe",
+        "bin/clang-cpp.exe",
+        "bin/clang-cl.exe",
+    ] + ALL_DLLS,
+)
+
+filegroup(
+    name = "clang-cl",
+    srcs = [
+        "bin/clang-cl.exe",
+    ] + ALL_DLLS,
+)
+
+filegroup(
+    name = "llvm-ml",
+    srcs = [
+        "bin/llvm-ml.exe",
+    ] + ALL_DLLS,
+)
+
+filegroup(
+    name = "ld",
+    # a set of 4 identical binaries?
+    srcs = ["bin/ld.lld.exe", "bin/ld64.lld.exe", "lld-link.exe", "lld.exe"] + ALL_DLLS,
+)
+
+filegroup(
+    name = "lld-link",
+    srcs = [
+        "bin/lld-link.exe",
+    ] + ALL_DLLS,
+)
+
+filegroup(
+    name = "llvm-lib",
+    srcs = [
+        "bin/llvm-lib.exe",
+    ] + ALL_DLLS,
+)
+
+filegroup(
+    name = "include",
+    srcs = glob([
+        "include/**/c++/**",
+        "lib/clang/*/include/**",
+    ]),
+)
+
+filegroup(
+  name = "all_includes",
+  srcs = glob(["include/**"]),
+)
+
+filegroup(
+    name = "bin",
+    srcs = glob(["bin/**"]),
+)
+
+filegroup(
+    name = "lib",
+    srcs = glob(
+        [
+            "lib/**/*.lib",
+        ],
+        exclude = [
+            "lib/LLVM*.lib",
+            "lib/clang*.lib",
+            "lib/lld*.lib",
+        ],
+    ),
+)
+
+filegroup(
+    name = "dll",
+    srcs = ALL_DLLS,
+)
+
+filegroup(
+    name = "ar",
+    srcs = ["bin/llvm-ar.exe"] + ALL_DLLS,
+)
+
+filegroup(
+    name = "as",
+    srcs = [
+        "bin/clang.exe",
+        "bin/llvm-as.exe",
+    ] + ALL_DLLS,
+)
+
+filegroup(
+    name = "nm",
+    srcs = ["bin/llvm-nm.exe"] + ALL_DLLS,
+)
+
+filegroup(
+    name = "objcopy",
+    srcs = ["bin/llvm-objcopy.exe"] + ALL_DLLS,
+)
+
+filegroup(
+    name = "objdump",
+    srcs = ["bin/llvm-objdump.exe"] + ALL_DLLS,
+)
+
+filegroup(
+    name = "profdata",
+    srcs = ["bin/llvm-profdata.exe"] + ALL_DLLS,
+)
+
+filegroup(
+    name = "dwp",
+    srcs = ["bin/llvm-dwp.exe"] + ALL_DLLS,
+)
+
+filegroup(
+    name = "ranlib",
+    srcs = ["bin/llvm-ranlib.exe"] + ALL_DLLS,
+)
+
+filegroup(
+    name = "readelf",
+    srcs = ["bin/llvm-readelf.exe"] + ALL_DLLS,
+)
+
+filegroup(
+    name = "strip",
+    srcs = ["bin/llvm-strip.exe"] + ALL_DLLS,
+)
+
+filegroup(
+    name = "symbolizer",
+    srcs = ["bin/llvm-symbolizer.exe"] + ALL_DLLS,
+)
+
+filegroup(
+    name = "clang-tidy",
+    srcs = ["bin/clang-tidy.exe"] + ALL_DLLS,
+)
diff --git a/toolchain/cc_toolchain_config.bzl b/toolchain/cc_toolchain_config.bzl
index c1b0d9226..f5cc8b51e 100644
--- a/toolchain/cc_toolchain_config.bzl
+++ b/toolchain/cc_toolchain_config.bzl
@@ -89,6 +89,14 @@ def cc_toolchain_config(
             "clang",
             "glibc_unknown",
         ),
+        "windows-x86_64": (
+            "clang-x86_64-windows",
+            "k8",
+            "msvc",
+            "clang",
+            "windows_x86_64",
+            "windows_x86_64",
+        ),
     }[target_os_arch_key]
 
     # Unfiltered compiler flags; these are placed at the end of the command
diff --git a/toolchain/internal/common.bzl b/toolchain/internal/common.bzl
index ff94bfb22..d3a7d631c 100644
--- a/toolchain/internal/common.bzl
+++ b/toolchain/internal/common.bzl
@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-SUPPORTED_TARGETS = [("linux", "x86_64"), ("linux", "aarch64"), ("darwin", "x86_64"), ("darwin", "aarch64")]
+SUPPORTED_TARGETS = [("linux", "x86_64"), ("linux", "aarch64"), ("darwin", "x86_64"), ("darwin", "aarch64"), ("windows", "x86_64")]
 
 # Map of tool name to its symlinked name in the tools directory.
 # See tool_paths in toolchain/cc_toolchain_config.bzl.
@@ -104,7 +104,7 @@ def os(rctx):
 
     name = rctx.attr.exec_os
     if name:
-        if name in ("linux", "darwin"):
+        if name in ("linux", "darwin", "windows"):
             return name
         else:
             fail("Unsupported value for exec_os: %s" % name)
@@ -120,7 +120,7 @@ def os(rctx):
 
 def os_bzl(os):
     # Return the OS string as used in bazel platform constraints.
-    return {"darwin": "osx", "linux": "linux"}[os]
+    return {"darwin": "osx", "linux": "linux", "windows": "windows"}[os]
 
 def arch(rctx):
     arch = rctx.attr.exec_arch
diff --git a/toolchain/internal/configure.bzl b/toolchain/internal/configure.bzl
index 6e40059cf..6840d318a 100644
--- a/toolchain/internal/configure.bzl
+++ b/toolchain/internal/configure.bzl
@@ -61,9 +61,6 @@ def llvm_config_impl(rctx):
     _check_os_arch_keys(rctx.attr.cxx_builtin_include_directories)
 
     os = _os(rctx)
-    if os == "windows":
-        _empty_repository(rctx)
-        return
     arch = _arch(rctx)
 
     if not rctx.attr.toolchain_roots:
@@ -311,6 +308,7 @@ def _cc_toolchain_str(
         "darwin-aarch64": "aarch64-apple-macosx",
         "linux-aarch64": "aarch64-unknown-linux-gnu",
         "linux-x86_64": "x86_64-unknown-linux-gnu",
+        "windows-x86_64": "x86_64-pc-windows-msvc",
     }[target_pair]
     cxx_builtin_include_directories = [
         toolchain_path_prefix + "include/c++/v1",
@@ -338,7 +336,7 @@ def _cc_toolchain_str(
             _join(sysroot_prefix, "/System/Library/Frameworks"),
         ])
     else:
-        fail("Unreachable")
+        pass
 
     cxx_builtin_include_directories.extend(toolchain_info.additional_include_dirs_dict.get(target_pair, []))
 
@@ -545,7 +543,13 @@ cc_toolchain(
         major_llvm_version = major_llvm_version,
     )
 
+def _extension(os):
+    if os == "windows":
+        return ".exe"
+    return ""
+
 def _convenience_targets_str(rctx, use_absolute_paths, llvm_dist_rel_path, llvm_dist_label_prefix, exec_dl_ext):
+    ext = _extension(_os(rctx))
     if use_absolute_paths:
         llvm_dist_label_prefix = ":"
         filenames = []
@@ -553,7 +557,7 @@ def _convenience_targets_str(rctx, use_absolute_paths, llvm_dist_rel_path, llvm_
             filename = "lib/{}.{}".format(libname, exec_dl_ext)
             filenames.append(filename)
         for toolname in _aliased_tools:
-            filename = "bin/{}".format(toolname)
+            filename = "bin/{}{}".format(toolname, ext)
             filenames.append(filename)
 
         for filename in filenames:
@@ -570,6 +574,7 @@ cc_import(
 
     tool_target_strs = []
     for name in _aliased_tools:
+        name = name + ext
         template = """
 native_binary(
     name = "{name}",
diff --git a/toolchain/internal/release_name.bzl b/toolchain/internal/release_name.bzl
index e3d4a540d..a56adabcc 100755
--- a/toolchain/internal/release_name.bzl
+++ b/toolchain/internal/release_name.bzl
@@ -46,6 +46,16 @@ def _darwin(llvm_version, arch):
     )
 
 def _windows(llvm_version, arch):
+    major_llvm_version = _major_llvm_version(llvm_version)
+    if major_llvm_version >= 18 and arch.endswith("64"):
+        arch = "x86_64"
+        suffix = "pc-windows-msvc"
+        return "clang+llvm-{llvm_version}-{arch}-{suffix}.tar.xz".format(
+            llvm_version = llvm_version,
+            arch = arch,
+            suffix = suffix,
+        )
+
     if arch.endswith("64"):
         win_arch = "win64"
     else:
diff --git a/toolchain/internal/repo.bzl b/toolchain/internal/repo.bzl
index 27012db6f..3b2899d02 100644
--- a/toolchain/internal/repo.bzl
+++ b/toolchain/internal/repo.bzl
@@ -291,14 +291,17 @@ llvm_config_attrs.update({
 def llvm_repo_impl(rctx):
     os = _os(rctx)
     if os == "windows":
-        rctx.file("BUILD.bazel", executable = False)
-        return None
-
-    rctx.file(
-        "BUILD.bazel",
-        content = rctx.read(Label("//toolchain:BUILD.llvm_repo")),
-        executable = False,
-    )
+        rctx.file(
+            "BUILD.bazel",
+            content = rctx.read(Label("//toolchain:BUILD.llvm_repo_windows")),
+            executable = False,
+        )
+    else:
+        rctx.file(
+            "BUILD.bazel",
+            content = rctx.read(Label("//toolchain:BUILD.llvm_repo")),
+            executable = False,
+        )
 
     updated_attrs = _download_llvm(rctx)