diff --git a/clang-tools-extra/clangd/URI.cpp b/clang-tools-extra/clangd/URI.cpp
--- a/clang-tools-extra/clangd/URI.cpp
+++ b/clang-tools-extra/clangd/URI.cpp
@@ -26,6 +26,15 @@
                                              llvm::inconvertibleErrorCode());
 }
 
+bool isWindowsPath(llvm::StringRef Path) {
+  return Path.size() > 1 && llvm::isAlpha(Path[0]) && Path[1] == ':';
+}
+
+bool isNetworkPath(llvm::StringRef Path) {
+  return Path.size() > 2 && Path[0] == Path[1] &&
+         llvm::sys::path::is_separator(Path[0]);
+}
+
 /// This manages file paths in the file system. All paths in the scheme
 /// are absolute (with leading '/').
 /// Note that this scheme is hardcoded into the library and not registered in
@@ -33,28 +42,40 @@
 class FileSystemScheme : public URIScheme {
 public:
   llvm::Expected<std::string>
-  getAbsolutePath(llvm::StringRef /*Authority*/, llvm::StringRef Body,
+  getAbsolutePath(llvm::StringRef Authority, llvm::StringRef Body,
                   llvm::StringRef /*HintPath*/) const override {
     if (!Body.startswith("/"))
       return make_string_error("File scheme: expect body to be an absolute "
                                "path starting with '/': " +
                                Body);
-    // For Windows paths e.g. /X:
-    if (Body.size() > 2 && Body[0] == '/' && Body[2] == ':')
+    llvm::SmallString<128> Path;
+    if (!Authority.empty()) {
+      // Windows UNC paths e.g. file://server/share => \\server\share
+      ("//" + Authority).toVector(Path);
+    } else if (isWindowsPath(Body.substr(1))) {
+      // Windows paths e.g. file:///X:/path => X:\path
       Body.consume_front("/");
-    llvm::SmallVector<char, 16> Path(Body.begin(), Body.end());
+    }
+    Path.append(Body);
     llvm::sys::path::native(Path);
-    return std::string(Path.begin(), Path.end());
+    return std::string(Path);
   }
 
   llvm::Expected<URI>
   uriFromAbsolutePath(llvm::StringRef AbsolutePath) const override {
     std::string Body;
-    // For Windows paths e.g. X:
-    if (AbsolutePath.size() > 1 && AbsolutePath[1] == ':')
+    llvm::StringRef Authority;
+    llvm::StringRef Root = llvm::sys::path::root_name(AbsolutePath);
+    if (isNetworkPath(Root)) {
+      // Windows UNC paths e.g. \\server\share => file://server/share
+      Authority = Root.drop_front(2);
+      AbsolutePath.consume_front(Root);
+    } else if (isWindowsPath(Root)) {
+      // Windows paths e.g. X:\path => file:///X:/path
       Body = "/";
+    }
     Body += llvm::sys::path::convert_to_slash(AbsolutePath);
-    return URI("file", /*Authority=*/"", Body);
+    return URI("file", Authority, Body);
   }
 };
 
@@ -96,13 +117,13 @@
 void percentEncode(llvm::StringRef Content, std::string &Out) {
   std::string Result;
   for (unsigned char C : Content)
-    if (shouldEscape(C))
-    {
+    if (shouldEscape(C)) {
       Out.push_back('%');
       Out.push_back(llvm::hexdigit(C / 16));
       Out.push_back(llvm::hexdigit(C % 16));
-    } else
-    { Out.push_back(C); }
+    } else {
+      Out.push_back(C);
+    }
 }
 
 /// Decodes a string according to percent-encoding.
diff --git a/clang-tools-extra/clangd/unittests/URITests.cpp b/clang-tools-extra/clangd/unittests/URITests.cpp
--- a/clang-tools-extra/clangd/unittests/URITests.cpp
+++ b/clang-tools-extra/clangd/unittests/URITests.cpp
@@ -76,6 +76,16 @@
 #endif
 }
 
+TEST(URITest, CreateUNC) {
+#ifdef _WIN32
+  EXPECT_THAT(createOrDie("\\\\test.org\\x\\y\\z"), "file://test.org/x/y/z");
+  EXPECT_THAT(createOrDie("\\\\10.0.0.1\\x\\y\\z"), "file://10.0.0.1/x/y/z");
+#else
+  EXPECT_THAT(createOrDie("//test.org/x/y/z"), "file://test.org/x/y/z");
+  EXPECT_THAT(createOrDie("//10.0.0.1/x/y/z"), "file://10.0.0.1/x/y/z");
+#endif
+}
+
 TEST(URITest, FailedCreate) {
   EXPECT_ERROR(URI::create("/x/y/z", "no"));
   // Path has to be absolute.
@@ -127,15 +137,32 @@
   EXPECT_THAT(resolveOrDie(parseOrDie("file:///c:/x/y/z")), "c:\\x\\y\\z");
 #else
   EXPECT_EQ(resolveOrDie(parseOrDie("file:/a/b/c")), "/a/b/c");
-  EXPECT_EQ(resolveOrDie(parseOrDie("file://auth/a/b/c")), "/a/b/c");
+  EXPECT_EQ(resolveOrDie(parseOrDie("file://auth/a/b/c")), "//auth/a/b/c");
   EXPECT_THAT(resolveOrDie(parseOrDie("file://au%3dth/%28x%29/y/%20z")),
-              "/(x)/y/ z");
+              "//au=th/(x)/y/ z");
   EXPECT_THAT(resolveOrDie(parseOrDie("file:///c:/x/y/z")), "c:/x/y/z");
 #endif
   EXPECT_EQ(resolveOrDie(parseOrDie("unittest:///a"), testPath("x")),
             testPath("a"));
 }
 
+TEST(URITest, ResolveUNC) {
+#ifdef _WIN32
+  EXPECT_THAT(resolveOrDie(parseOrDie("file://example.com/x/y/z")),
+              "\\\\example.com\\x\\y\\z");
+  EXPECT_THAT(resolveOrDie(parseOrDie("file://127.0.0.1/x/y/z")),
+              "\\\\127.0.0.1\\x\\y\\z");
+  // Ensure non-traditional file URI still resolves to correct UNC path.
+  EXPECT_THAT(resolveOrDie(parseOrDie("file:////127.0.0.1/x/y/z")),
+              "\\\\127.0.0.1\\x\\y\\z");
+#else
+  EXPECT_THAT(resolveOrDie(parseOrDie("file://example.com/x/y/z")),
+              "//example.com/x/y/z");
+  EXPECT_THAT(resolveOrDie(parseOrDie("file://127.0.0.1/x/y/z")),
+              "//127.0.0.1/x/y/z");
+#endif
+}
+
 std::string resolvePathOrDie(llvm::StringRef AbsPath,
                              llvm::StringRef HintPath = "") {
   auto Path = URI::resolvePath(AbsPath, HintPath);