diff --git a/ipc/ipc_message_utils.h b/ipc/ipc_message_utils.h
index a27463594bcd06..0d9d5c204ecf6b 100644
--- a/ipc/ipc_message_utils.h
+++ b/ipc/ipc_message_utils.h
@@ -982,6 +982,8 @@ struct ParamTraits<std::unique_ptr<P>> {
   }
 };
 
+// absl types ParamTraits
+
 template <class P>
 struct ParamTraits<absl::optional<P>> {
   typedef absl::optional<P> param_type;
@@ -1013,6 +1015,18 @@ struct ParamTraits<absl::optional<P>> {
   }
 };
 
+template <>
+struct ParamTraits<absl::monostate> {
+  typedef absl::monostate param_type;
+  static void Write(base::Pickle* m, const param_type& p) {}
+  static bool Read(const base::Pickle* m,
+                   base::PickleIterator* iter,
+                   param_type* r) {
+    return true;
+  }
+  static void Log(const param_type& p, std::string* l) { l->append("()"); }
+};
+
 // base/util types ParamTraits
 
 template <typename TypeMarker, typename WrappedType, WrappedType kInvalidValue>
diff --git a/remoting/base/result.h b/remoting/base/result.h
index 6775e0dd143997..ce6a842d33c332 100644
--- a/remoting/base/result.h
+++ b/remoting/base/result.h
@@ -10,6 +10,7 @@
 
 #include "base/check.h"
 #include "third_party/abseil-cpp/absl/types/optional.h"
+#include "third_party/abseil-cpp/absl/types/variant.h"
 
 // Result<SuccessType, ErrorType> represents the success or failure of an
 // operation, along with either the success value or error details.
@@ -127,18 +128,16 @@ namespace remoting {
 // state or error state, respectively.
 class SuccessTag {};
 class ErrorTag {};
-// Monostate can be used for SuccessType or ErrorType to indicate that there is
-// no data for that state. Thus, Result<SomeType, Monostate> is somewhat
-// analogous to absl::optional<SomeType>, and Result<Monostate, Monostate> is
-// effectively a (2-byte) boolean. Result<Monostate, ErrorType> can be useful
-// for cases where an operation can fail, but there is no return value in the
-// success case.
-// TODO(rkjnsn): Replace with std::monostate once C++17 is allowed.
-class Monostate {};
+// absl::Monostate can be used for SuccessType or ErrorType to indicate that
+// there is no data for that state. Thus, Result<SomeType, Monostate> is
+// somewhat analogous to absl::optional<SomeType>, and Result<Monostate,
+// Monostate> is effectively a (2-byte) boolean. Result<Monostate, ErrorType>
+// can be useful for cases where an operation can fail, but there is no return
+// value in the success case.
 
 constexpr SuccessTag kSuccessTag = SuccessTag();
 constexpr ErrorTag kErrorTag = ErrorTag();
-constexpr Monostate kMonostate = Monostate();
+constexpr absl::monostate kMonostate = absl::monostate();
 
 namespace internal {
 
diff --git a/remoting/host/chromoting_messages.h b/remoting/host/chromoting_messages.h
index e9c72f4c267dab..44b71f718e5c74 100644
--- a/remoting/host/chromoting_messages.h
+++ b/remoting/host/chromoting_messages.h
@@ -49,7 +49,7 @@ IPC_MESSAGE_CONTROL(ChromotingDesktopNetworkMsg_KeyboardChanged,
 IPC_MESSAGE_CONTROL(
     ChromotingDesktopNetworkMsg_FileResult,
     uint64_t /* file_id */,
-    remoting::protocol::FileTransferResult<remoting::Monostate> /* result */)
+    remoting::protocol::FileTransferResult<absl::monostate> /* result */)
 
 // Carries the result of a read-file operation on the file identified by
 // |file_id|. |result| is the filename and size of the selected file. If
diff --git a/remoting/host/chromoting_param_traits.cc b/remoting/host/chromoting_param_traits.cc
index a86b9b5b58d5eb..56aec35e61525a 100644
--- a/remoting/host/chromoting_param_traits.cc
+++ b/remoting/host/chromoting_param_traits.cc
@@ -79,22 +79,4 @@ void ParamTraits<remoting::protocol::FileTransfer_Error>::Log(
       base::StringPrintf("FileTransfer Error: %s", formatted.str().c_str()));
 }
 
-// remoting::Monostate
-
-// static
-void IPC::ParamTraits<remoting::Monostate>::Write(base::Pickle*,
-                                                  const param_type&) {}
-
-// static
-bool ParamTraits<remoting::Monostate>::Read(const base::Pickle*,
-                                            base::PickleIterator*,
-                                            param_type*) {
-  return true;
-}
-
-// static
-void ParamTraits<remoting::Monostate>::Log(const param_type&, std::string* l) {
-  l->append("()");
-}
-
 }  // namespace IPC
diff --git a/remoting/host/chromoting_param_traits.h b/remoting/host/chromoting_param_traits.h
index ffe533435ddcef..b85c58728b3509 100644
--- a/remoting/host/chromoting_param_traits.h
+++ b/remoting/host/chromoting_param_traits.h
@@ -33,16 +33,6 @@ struct ParamTraits<remoting::protocol::FileTransfer_Error> {
   static void Log(const param_type& p, std::string* l);
 };
 
-template <>
-struct ParamTraits<remoting::Monostate> {
-  typedef remoting::Monostate param_type;
-  static void Write(base::Pickle* m, const param_type& p);
-  static bool Read(const base::Pickle* m,
-                   base::PickleIterator* iter,
-                   param_type* p);
-  static void Log(const param_type& p, std::string* l);
-};
-
 template <typename SuccessType, typename ErrorType>
 struct ParamTraits<remoting::Result<SuccessType, ErrorType>> {
   typedef remoting::Result<SuccessType, ErrorType> param_type;
diff --git a/remoting/host/file_transfer/ensure_user.h b/remoting/host/file_transfer/ensure_user.h
index f358e81344f3b9..561d329871e434 100644
--- a/remoting/host/file_transfer/ensure_user.h
+++ b/remoting/host/file_transfer/ensure_user.h
@@ -17,7 +17,7 @@ namespace remoting {
 // user is on the log-in screen, an error of type NOT_LOGGED_IN will be
 // returned. If something else goes wrong, the error type will be
 // UNEXPECTED_ERROR.
-protocol::FileTransferResult<Monostate> EnsureUserContext();
+protocol::FileTransferResult<absl::monostate> EnsureUserContext();
 
 }  // namespace remoting
 
diff --git a/remoting/host/file_transfer/ensure_user_mac.cc b/remoting/host/file_transfer/ensure_user_mac.cc
index da6c4b82ecd04e..6109d0da762344 100644
--- a/remoting/host/file_transfer/ensure_user_mac.cc
+++ b/remoting/host/file_transfer/ensure_user_mac.cc
@@ -10,7 +10,7 @@
 
 namespace remoting {
 
-protocol::FileTransferResult<Monostate> EnsureUserContext() {
+protocol::FileTransferResult<absl::monostate> EnsureUserContext() {
   // Make sure we're not on the log-in screen.
   if (getuid() == 0) {
     LOG(ERROR) << "Cannot transfer files on log-in screen.";
diff --git a/remoting/host/file_transfer/ensure_user_no_op.cc b/remoting/host/file_transfer/ensure_user_no_op.cc
index 4905b97cc220a6..f04c8b5acb9ccb 100644
--- a/remoting/host/file_transfer/ensure_user_no_op.cc
+++ b/remoting/host/file_transfer/ensure_user_no_op.cc
@@ -6,7 +6,7 @@
 
 namespace remoting {
 
-protocol::FileTransferResult<Monostate> EnsureUserContext() {
+protocol::FileTransferResult<absl::monostate> EnsureUserContext() {
   return kSuccessTag;
 }
 
diff --git a/remoting/host/file_transfer/ensure_user_win.cc b/remoting/host/file_transfer/ensure_user_win.cc
index 3ecfe197899132..74270beaacd8e6 100644
--- a/remoting/host/file_transfer/ensure_user_win.cc
+++ b/remoting/host/file_transfer/ensure_user_win.cc
@@ -12,7 +12,7 @@
 
 namespace remoting {
 
-protocol::FileTransferResult<Monostate> EnsureUserContext() {
+protocol::FileTransferResult<absl::monostate> EnsureUserContext() {
   // Impersonate the currently logged-in user, or fail if there is none.
   HANDLE user_token = nullptr;
   if (!WTSQueryUserToken(WTS_CURRENT_SESSION, &user_token)) {
diff --git a/remoting/host/file_transfer/file_chooser_win.cc b/remoting/host/file_transfer/file_chooser_win.cc
index 9ae968700e0359..b1c2b1312d6607 100644
--- a/remoting/host/file_transfer/file_chooser_win.cc
+++ b/remoting/host/file_transfer/file_chooser_win.cc
@@ -112,7 +112,7 @@ class FileChooserWindows : public FileChooser,
   void OnObjectSignaled(HANDLE object) override;
 
  private:
-  FileTransferResult<Monostate> LaunchChooserProcess();
+  FileTransferResult<absl::monostate> LaunchChooserProcess();
 
   ResultCallback callback_;
   base::Process process_;
@@ -126,7 +126,7 @@ FileChooserWindows::FileChooserWindows(
     : callback_(std::move(callback)) {}
 
 void FileChooserWindows::Show() {
-  FileTransferResult<Monostate> result = LaunchChooserProcess();
+  FileTransferResult<absl::monostate> result = LaunchChooserProcess();
 
   if (!result) {
     base::SequencedTaskRunnerHandle::Get()->PostTask(
@@ -180,7 +180,7 @@ void FileChooserWindows::OnObjectSignaled(HANDLE object) {
   std::move(callback_).Run(std::move(result));
 }
 
-FileTransferResult<Monostate> FileChooserWindows::LaunchChooserProcess() {
+FileTransferResult<absl::monostate> FileChooserWindows::LaunchChooserProcess() {
   base::LaunchOptions launch_options;
 
   FileTransferResult<ScopedHandle> current_user =
diff --git a/remoting/host/file_transfer/file_operations.h b/remoting/host/file_transfer/file_operations.h
index 32b4b1745a1114..6b9e94ec155665 100644
--- a/remoting/host/file_transfer/file_operations.h
+++ b/remoting/host/file_transfer/file_operations.h
@@ -45,7 +45,7 @@ class FileOperations {
 
   class Reader {
    public:
-    using OpenResult = protocol::FileTransferResult<Monostate>;
+    using OpenResult = protocol::FileTransferResult<absl::monostate>;
     using OpenCallback = base::OnceCallback<void(OpenResult result)>;
 
     // On success, |result| will contain the read data, or an empty vector on
@@ -71,7 +71,7 @@ class FileOperations {
 
   class Writer {
    public:
-    using Result = protocol::FileTransferResult<Monostate>;
+    using Result = protocol::FileTransferResult<absl::monostate>;
     using Callback = base::OnceCallback<void(Result result)>;
 
     // Destructing before the file is completely written and closed will
diff --git a/remoting/host/file_transfer/ipc_file_operations.h b/remoting/host/file_transfer/ipc_file_operations.h
index 07fae0a284fa4b..09d848c8773dc4 100644
--- a/remoting/host/file_transfer/ipc_file_operations.h
+++ b/remoting/host/file_transfer/ipc_file_operations.h
@@ -43,7 +43,7 @@ class IpcFileOperations : public FileOperations {
   // Handles responses to file operations requests.
   class ResultHandler {
    public:
-    using Result = protocol::FileTransferResult<Monostate>;
+    using Result = protocol::FileTransferResult<absl::monostate>;
     using InfoResult =
         protocol::FileTransferResult<std::tuple<base::FilePath, uint64_t>>;
     using DataResult =
diff --git a/remoting/host/file_transfer/local_file_operations.cc b/remoting/host/file_transfer/local_file_operations.cc
index dff9c4622c4156..c3059fb9007c34 100644
--- a/remoting/host/file_transfer/local_file_operations.cc
+++ b/remoting/host/file_transfer/local_file_operations.cc
@@ -77,7 +77,7 @@ class LocalFileReader : public FileOperations::Reader {
 
  private:
   void OnEnsureUserResult(OpenCallback callback,
-                          protocol::FileTransferResult<Monostate> result);
+                          protocol::FileTransferResult<absl::monostate> result);
   void OnFileChooserResult(OpenCallback callback, FileChooser::Result result);
   void OnOpenResult(OpenCallback callback, base::File::Error error);
   void OnGetInfoResult(OpenCallback callback,
@@ -196,7 +196,7 @@ FileOperations::State LocalFileReader::state() const {
 
 void LocalFileReader::OnEnsureUserResult(
     FileOperations::Reader::OpenCallback callback,
-    protocol::FileTransferResult<Monostate> result) {
+    protocol::FileTransferResult<absl::monostate> result) {
   if (!result) {
     SetState(FileOperations::kFailed);
     std::move(callback).Run(std::move(result.error()));
@@ -313,7 +313,7 @@ void LocalFileWriter::Open(const base::FilePath& filename, Callback callback) {
   base::PostTaskAndReplyWithResult(
       file_task_runner_.get(), FROM_HERE, base::BindOnce([] {
         return EnsureUserContext().AndThen(
-            [](Monostate) { return GetDesktopDirectory(); });
+            [](absl::monostate) { return GetDesktopDirectory(); });
       }),
       base::BindOnce(&LocalFileWriter::OnGetTargetDirectoryResult,
                      weak_ptr_factory_.GetWeakPtr(), filename,
diff --git a/ui/accessibility/platform/inspect/ax_call_statement_invoker_auralinux.h b/ui/accessibility/platform/inspect/ax_call_statement_invoker_auralinux.h
index 56c2d4b4772357..823bd271f05afe 100644
--- a/ui/accessibility/platform/inspect/ax_call_statement_invoker_auralinux.h
+++ b/ui/accessibility/platform/inspect/ax_call_statement_invoker_auralinux.h
@@ -6,7 +6,6 @@
 #define UI_ACCESSIBILITY_PLATFORM_INSPECT_AX_CALL_STATEMENT_INVOKER_AURALINUX_H_
 
 #include <atspi/atspi.h>
-#include <variant>
 
 #include "base/memory/raw_ptr.h"
 #include "third_party/abseil-cpp/absl/types/variant.h"
@@ -19,7 +18,7 @@ namespace ui {
 class AXPropertyNode;
 
 using Target =
-    absl::variant<std::monostate, std::string, int, const AtspiAccessible*>;
+    absl::variant<absl::monostate, std::string, int, const AtspiAccessible*>;
 
 // Optional tri-state object.
 using AXOptionalObject = ui::AXOptional<Target>;