diff --git a/quiche/quic/core/http/http_constants.cc b/quiche/quic/core/http/http_constants.cc
index 03dea06..a22620d 100644
--- a/quiche/quic/core/http/http_constants.cc
+++ b/quiche/quic/core/http/http_constants.cc
@@ -18,6 +18,7 @@
     RETURN_STRING_LITERAL(SETTINGS_MAX_FIELD_SECTION_SIZE);
     RETURN_STRING_LITERAL(SETTINGS_QPACK_BLOCKED_STREAMS);
     RETURN_STRING_LITERAL(SETTINGS_H3_DATAGRAM_DRAFT04);
+    RETURN_STRING_LITERAL(SETTINGS_H3_DATAGRAM_DRAFT09);
     RETURN_STRING_LITERAL(SETTINGS_WEBTRANS_DRAFT00);
     RETURN_STRING_LITERAL(SETTINGS_ENABLE_CONNECT_PROTOCOL);
   }
diff --git a/quiche/quic/core/http/http_constants.h b/quiche/quic/core/http/http_constants.h
index ee0a3f3..9e1a696 100644
--- a/quiche/quic/core/http/http_constants.h
+++ b/quiche/quic/core/http/http_constants.h
@@ -40,6 +40,8 @@
   SETTINGS_QPACK_BLOCKED_STREAMS = 0x07,
   // draft-ietf-masque-h3-datagram-04.
   SETTINGS_H3_DATAGRAM_DRAFT04 = 0xffd277,
+  // draft-ietf-masque-h3-datagram-09.
+  SETTINGS_H3_DATAGRAM_DRAFT09 = 0x33,
   // draft-ietf-webtrans-http3-00
   SETTINGS_WEBTRANS_DRAFT00 = 0x2b603742,
   // draft-ietf-httpbis-h3-websockets
diff --git a/quiche/quic/core/http/quic_spdy_session.cc b/quiche/quic/core/http/quic_spdy_session.cc
index 12efa66..af40f36 100644
--- a/quiche/quic/core/http/quic_spdy_session.cc
+++ b/quiche/quic/core/http/quic_spdy_session.cc
@@ -516,10 +516,19 @@
   settings_.values[SETTINGS_MAX_FIELD_SECTION_SIZE] =
       max_inbound_header_list_size_;
   if (version().UsesHttp3()) {
-    HttpDatagramSupport local_http_datagram_support =
-        LocalHttpDatagramSupport();
-    if (local_http_datagram_support == HttpDatagramSupport::kDraft04) {
-      settings_.values[SETTINGS_H3_DATAGRAM_DRAFT04] = 1;
+    switch (LocalHttpDatagramSupport()) {
+      case HttpDatagramSupport::kNone:
+        break;
+      case HttpDatagramSupport::kDraft04:
+        settings_.values[SETTINGS_H3_DATAGRAM_DRAFT04] = 1;
+        break;
+      case HttpDatagramSupport::kDraft09:
+        settings_.values[SETTINGS_H3_DATAGRAM_DRAFT09] = 1;
+        break;
+      case HttpDatagramSupport::kDraft04And09:
+        settings_.values[SETTINGS_H3_DATAGRAM_DRAFT04] = 1;
+        settings_.values[SETTINGS_H3_DATAGRAM_DRAFT09] = 1;
+        break;
     }
   }
   if (WillNegotiateWebTransport()) {
@@ -1139,7 +1148,8 @@
       case SETTINGS_H3_DATAGRAM_DRAFT04: {
         HttpDatagramSupport local_http_datagram_support =
             LocalHttpDatagramSupport();
-        if (local_http_datagram_support != HttpDatagramSupport::kDraft04) {
+        if (local_http_datagram_support != HttpDatagramSupport::kDraft04 &&
+            local_http_datagram_support != HttpDatagramSupport::kDraft04And09) {
           break;
         }
         QUIC_DVLOG(1) << ENDPOINT
@@ -1151,11 +1161,33 @@
         if (!VerifySettingIsZeroOrOne(id, value)) {
           return false;
         }
-        if (value) {
+        if (value && http_datagram_support_ != HttpDatagramSupport::kDraft09) {
+          // If both draft-04 and draft-09 are supported, use draft-09.
           http_datagram_support_ = HttpDatagramSupport::kDraft04;
         }
         break;
       }
+      case SETTINGS_H3_DATAGRAM_DRAFT09: {
+        HttpDatagramSupport local_http_datagram_support =
+            LocalHttpDatagramSupport();
+        if (local_http_datagram_support != HttpDatagramSupport::kDraft09 &&
+            local_http_datagram_support != HttpDatagramSupport::kDraft04And09) {
+          break;
+        }
+        QUIC_DVLOG(1) << ENDPOINT
+                      << "SETTINGS_H3_DATAGRAM_DRAFT09 received with value "
+                      << value;
+        if (!version().UsesHttp3()) {
+          break;
+        }
+        if (!VerifySettingIsZeroOrOne(id, value)) {
+          return false;
+        }
+        if (value) {
+          http_datagram_support_ = HttpDatagramSupport::kDraft09;
+        }
+        break;
+      }
       case SETTINGS_WEBTRANS_DRAFT00:
         if (!WillNegotiateWebTransport()) {
           break;
@@ -1790,6 +1822,10 @@
       return "None";
     case HttpDatagramSupport::kDraft04:
       return "Draft04";
+    case HttpDatagramSupport::kDraft09:
+      return "Draft09";
+    case HttpDatagramSupport::kDraft04And09:
+      return "Draft04And09";
   }
   return absl::StrCat("Unknown(", static_cast<int>(http_datagram_support), ")");
 }
diff --git a/quiche/quic/core/http/quic_spdy_session.h b/quiche/quic/core/http/quic_spdy_session.h
index a6418b9..25d3be0 100644
--- a/quiche/quic/core/http/quic_spdy_session.h
+++ b/quiche/quic/core/http/quic_spdy_session.h
@@ -120,6 +120,8 @@
 enum class HttpDatagramSupport : uint8_t {
   kNone,  // HTTP Datagrams are not supported for this session.
   kDraft04,
+  kDraft09,
+  kDraft04And09,  // Only used locally for sending, we only negotiate one draft.
 };
 
 QUIC_EXPORT_PRIVATE std::string HttpDatagramSupportToString(
diff --git a/quiche/quic/core/http/quic_spdy_session_test.cc b/quiche/quic/core/http/quic_spdy_session_test.cc
index 84b50c7..f854763 100644
--- a/quiche/quic/core/http/quic_spdy_session_test.cc
+++ b/quiche/quic/core/http/quic_spdy_session_test.cc
@@ -3388,6 +3388,13 @@
     case HttpDatagramSupport::kDraft04:
       settings.values[SETTINGS_H3_DATAGRAM_DRAFT04] = 1;
       break;
+    case HttpDatagramSupport::kDraft09:
+      settings.values[SETTINGS_H3_DATAGRAM_DRAFT09] = 1;
+      break;
+    case HttpDatagramSupport::kDraft04And09:
+      settings.values[SETTINGS_H3_DATAGRAM_DRAFT04] = 1;
+      settings.values[SETTINGS_H3_DATAGRAM_DRAFT09] = 1;
+      break;
   }
   std::string data = std::string(1, kControlStream) + EncodeSettings(settings);
   QuicStreamId stream_id =
@@ -3410,6 +3417,70 @@
       /*expected_datagram_supported=*/true);
 }
 
+TEST_P(QuicSpdySessionTestClient, HttpDatagramSettingLocal04Remote09) {
+  TestHttpDatagramSetting(
+      /*local_support=*/HttpDatagramSupport::kDraft04,
+      /*remote_support=*/HttpDatagramSupport::kDraft09,
+      /*expected_support=*/HttpDatagramSupport::kNone,
+      /*expected_datagram_supported=*/false);
+}
+
+TEST_P(QuicSpdySessionTestClient, HttpDatagramSettingLocal04Remote04And09) {
+  TestHttpDatagramSetting(
+      /*local_support=*/HttpDatagramSupport::kDraft04,
+      /*remote_support=*/HttpDatagramSupport::kDraft04And09,
+      /*expected_support=*/HttpDatagramSupport::kDraft04,
+      /*expected_datagram_supported=*/true);
+}
+
+TEST_P(QuicSpdySessionTestClient, HttpDatagramSettingLocal09Remote04) {
+  TestHttpDatagramSetting(
+      /*local_support=*/HttpDatagramSupport::kDraft09,
+      /*remote_support=*/HttpDatagramSupport::kDraft04,
+      /*expected_support=*/HttpDatagramSupport::kNone,
+      /*expected_datagram_supported=*/false);
+}
+
+TEST_P(QuicSpdySessionTestClient, HttpDatagramSettingLocal09Remote09) {
+  TestHttpDatagramSetting(
+      /*local_support=*/HttpDatagramSupport::kDraft09,
+      /*remote_support=*/HttpDatagramSupport::kDraft09,
+      /*expected_support=*/HttpDatagramSupport::kDraft09,
+      /*expected_datagram_supported=*/true);
+}
+
+TEST_P(QuicSpdySessionTestClient, HttpDatagramSettingLocal09Remote04And09) {
+  TestHttpDatagramSetting(
+      /*local_support=*/HttpDatagramSupport::kDraft09,
+      /*remote_support=*/HttpDatagramSupport::kDraft04And09,
+      /*expected_support=*/HttpDatagramSupport::kDraft09,
+      /*expected_datagram_supported=*/true);
+}
+
+TEST_P(QuicSpdySessionTestClient, HttpDatagramSettingLocal04And09Remote04) {
+  TestHttpDatagramSetting(
+      /*local_support=*/HttpDatagramSupport::kDraft04And09,
+      /*remote_support=*/HttpDatagramSupport::kDraft04,
+      /*expected_support=*/HttpDatagramSupport::kDraft04,
+      /*expected_datagram_supported=*/true);
+}
+
+TEST_P(QuicSpdySessionTestClient, HttpDatagramSettingLocal04And09Remote09) {
+  TestHttpDatagramSetting(
+      /*local_support=*/HttpDatagramSupport::kDraft04And09,
+      /*remote_support=*/HttpDatagramSupport::kDraft09,
+      /*expected_support=*/HttpDatagramSupport::kDraft09,
+      /*expected_datagram_supported=*/true);
+}
+
+TEST_P(QuicSpdySessionTestClient,
+       HttpDatagramSettingLocal04And09Remote04And09) {
+  TestHttpDatagramSetting(
+      /*local_support=*/HttpDatagramSupport::kDraft04And09,
+      /*remote_support=*/HttpDatagramSupport::kDraft04And09,
+      /*expected_support=*/HttpDatagramSupport::kDraft09,
+      /*expected_datagram_supported=*/true);
+}
 TEST_P(QuicSpdySessionTestClient, WebTransportSetting) {
   if (!version().UsesHttp3()) {
     return;
diff --git a/quiche/quic/core/http/quic_spdy_stream.cc b/quiche/quic/core/http/quic_spdy_stream.cc
index 4064d28..10d76af 100644
--- a/quiche/quic/core/http/quic_spdy_stream.cc
+++ b/quiche/quic/core/http/quic_spdy_stream.cc
@@ -1511,10 +1511,12 @@
   QuicByteCount prefix_size = 0;
   switch (spdy_session_->http_datagram_support()) {
     case HttpDatagramSupport::kDraft04:
+    case HttpDatagramSupport::kDraft09:
       prefix_size =
           QuicDataWriter::GetVarInt62Len(id() / kHttpDatagramStreamIdDivisor);
       break;
     case HttpDatagramSupport::kNone:
+    case HttpDatagramSupport::kDraft04And09:
       QUIC_BUG(GetMaxDatagramSize called with no datagram support)
           << "GetMaxDatagramSize() called when no HTTP/3 datagram support has "
              "been negotiated.  Support value: "
diff --git a/quiche/quic/core/http/quic_spdy_stream_test.cc b/quiche/quic/core/http/quic_spdy_stream_test.cc
index 80d9ee2..3c00c7b 100644
--- a/quiche/quic/core/http/quic_spdy_stream_test.cc
+++ b/quiche/quic/core/http/quic_spdy_stream_test.cc
@@ -3131,9 +3131,9 @@
     return;
   }
   InitializeWithPerspective(kShouldProcessData, Perspective::IS_CLIENT);
-  session_->set_local_http_datagram_support(HttpDatagramSupport::kDraft04);
+  session_->set_local_http_datagram_support(HttpDatagramSupport::kDraft09);
   QuicSpdySessionPeer::SetHttpDatagramSupport(session_.get(),
-                                              HttpDatagramSupport::kDraft04);
+                                              HttpDatagramSupport::kDraft09);
   headers_[":method"] = "CONNECT";
   headers_[":protocol"] = "webtransport";
   ProcessHeaders(false, headers_);
@@ -3171,9 +3171,9 @@
     return;
   }
   Initialize(kShouldProcessData);
-  session_->set_local_http_datagram_support(HttpDatagramSupport::kDraft04);
+  session_->set_local_http_datagram_support(HttpDatagramSupport::kDraft09);
   QuicSpdySessionPeer::SetHttpDatagramSupport(session_.get(),
-                                              HttpDatagramSupport::kDraft04);
+                                              HttpDatagramSupport::kDraft09);
   std::string http_datagram_payload = {1, 2, 3, 4, 5, 6};
   EXPECT_CALL(*connection_, SendMessage(1, _, false))
       .WillOnce(Return(MESSAGE_STATUS_SUCCESS));
@@ -3186,9 +3186,9 @@
     return;
   }
   Initialize(kShouldProcessData);
-  session_->set_local_http_datagram_support(HttpDatagramSupport::kDraft04);
+  session_->set_local_http_datagram_support(HttpDatagramSupport::kDraft09);
   QuicSpdySessionPeer::SetHttpDatagramSupport(session_.get(),
-                                              HttpDatagramSupport::kDraft04);
+                                              HttpDatagramSupport::kDraft09);
   EXPECT_GT(stream_->GetMaxDatagramSize(), 512u);
 }
 
diff --git a/quiche/quic/masque/masque_client_session.h b/quiche/quic/masque/masque_client_session.h
index 41c63a9..66c7e2e 100644
--- a/quiche/quic/masque/masque_client_session.h
+++ b/quiche/quic/masque/masque_client_session.h
@@ -125,7 +125,7 @@
   };
 
   HttpDatagramSupport LocalHttpDatagramSupport() override {
-    return HttpDatagramSupport::kDraft04;
+    return HttpDatagramSupport::kDraft09;
   }
 
   const ConnectUdpClientState* GetOrCreateConnectUdpClientState(
diff --git a/quiche/quic/masque/masque_server_session.h b/quiche/quic/masque/masque_server_session.h
index 922e710..59b33c2 100644
--- a/quiche/quic/masque/masque_server_session.h
+++ b/quiche/quic/masque/masque_server_session.h
@@ -97,7 +97,7 @@
   // From QuicSpdySession.
   bool OnSettingsFrame(const SettingsFrame& frame) override;
   HttpDatagramSupport LocalHttpDatagramSupport() override {
-    return HttpDatagramSupport::kDraft04;
+    return HttpDatagramSupport::kDraft09;
   }
 
   MasqueServerBackend* masque_server_backend_;  // Unowned.