diff --git a/quic/core/quic_dispatcher_test.cc b/quic/core/quic_dispatcher_test.cc
index 878dd75..16d2584 100644
--- a/quic/core/quic_dispatcher_test.cc
+++ b/quic/core/quic_dispatcher_test.cc
@@ -855,7 +855,6 @@
   static_assert(QUIC_ARRAYSIZE(kSupportedTransportVersions) == 6u,
                 "Supported versions out of sync");
   SetQuicReloadableFlag(quic_disable_version_39, false);
-  SetQuicReloadableFlag(quic_enable_version_43, true);
   SetQuicReloadableFlag(quic_enable_version_44, true);
   SetQuicReloadableFlag(quic_enable_version_46, true);
   SetQuicReloadableFlag(quic_enable_version_47, true);
@@ -1010,39 +1009,6 @@
                 SerializeCHLO(), CONNECTION_ID_PRESENT,
                 PACKET_4BYTE_PACKET_NUMBER, 1);
 
-  // Turn off version 43.
-  SetQuicReloadableFlag(quic_enable_version_43, false);
-  connection_id = TestConnectionId(++conn_id);
-  EXPECT_CALL(*dispatcher_, CreateQuicSession(connection_id, client_address,
-                                              QuicStringPiece("hq"), _))
-      .Times(0);
-  ProcessPacket(client_address, connection_id, true,
-                ParsedQuicVersion(PROTOCOL_QUIC_CRYPTO, QUIC_VERSION_43),
-                SerializeCHLO(), CONNECTION_ID_PRESENT,
-                PACKET_4BYTE_PACKET_NUMBER, 1);
-
-  // Turn on version 43.
-  SetQuicReloadableFlag(quic_enable_version_43, true);
-  connection_id = TestConnectionId(++conn_id);
-  EXPECT_CALL(*dispatcher_, CreateQuicSession(connection_id, client_address,
-                                              QuicStringPiece("hq"), _))
-      .WillOnce(testing::Return(CreateSession(
-          dispatcher_.get(), config_, connection_id, client_address,
-          &mock_helper_, &mock_alarm_factory_, &crypto_config_,
-          QuicDispatcherPeer::GetCache(dispatcher_.get()), &session1_)));
-  EXPECT_CALL(*reinterpret_cast<MockQuicConnection*>(session1_->connection()),
-              ProcessUdpPacket(_, _, _))
-      .WillOnce(WithArg<2>(
-          Invoke([this, connection_id](const QuicEncryptedPacket& packet) {
-            ValidatePacket(connection_id, packet);
-          })));
-  EXPECT_CALL(*dispatcher_,
-              ShouldCreateOrBufferPacketForConnection(connection_id, _));
-  ProcessPacket(client_address, connection_id, true,
-                ParsedQuicVersion(PROTOCOL_QUIC_CRYPTO, QUIC_VERSION_43),
-                SerializeCHLO(), CONNECTION_ID_PRESENT,
-                PACKET_4BYTE_PACKET_NUMBER, 1);
-
   // Turn off version 39.
   SetQuicReloadableFlag(quic_disable_version_39, true);
   connection_id = TestConnectionId(++conn_id);
@@ -2833,7 +2799,6 @@
   // because of QUIC_INVALID_STREAM_DATA.
 
   SetQuicReloadableFlag(quic_disable_version_39, false);
-  SetQuicReloadableFlag(quic_enable_version_43, true);
   ParsedQuicVersion chlo_version(PROTOCOL_QUIC_CRYPTO, QUIC_VERSION_43);
   chlo_.SetVersion(kVER, chlo_version);
   // Send a CHLO with v43. Dispatcher framer's version is set to v43.
diff --git a/quic/core/quic_version_manager.cc b/quic/core/quic_version_manager.cc
index 62b2e44..5874f92 100644
--- a/quic/core/quic_version_manager.cc
+++ b/quic/core/quic_version_manager.cc
@@ -18,7 +18,6 @@
       enable_version_47_(GetQuicReloadableFlag(quic_enable_version_47)),
       enable_version_46_(GetQuicReloadableFlag(quic_enable_version_46)),
       enable_version_44_(GetQuicReloadableFlag(quic_enable_version_44)),
-      enable_version_43_(GetQuicReloadableFlag(quic_enable_version_43)),
       disable_version_39_(GetQuicReloadableFlag(quic_disable_version_39)),
       allowed_supported_versions_(std::move(supported_versions)) {
   RefilterSupportedVersions();
@@ -42,13 +41,11 @@
       enable_version_47_ != GetQuicReloadableFlag(quic_enable_version_47) ||
       enable_version_46_ != GetQuicReloadableFlag(quic_enable_version_46) ||
       enable_version_44_ != GetQuicReloadableFlag(quic_enable_version_44) ||
-      enable_version_43_ != GetQuicReloadableFlag(quic_enable_version_43) ||
       disable_version_39_ != GetQuicReloadableFlag(quic_disable_version_39)) {
     enable_version_99_ = GetQuicReloadableFlag(quic_enable_version_99);
     enable_version_47_ = GetQuicReloadableFlag(quic_enable_version_47);
     enable_version_46_ = GetQuicReloadableFlag(quic_enable_version_46);
     enable_version_44_ = GetQuicReloadableFlag(quic_enable_version_44);
-    enable_version_43_ = GetQuicReloadableFlag(quic_enable_version_43);
     disable_version_39_ = GetQuicReloadableFlag(quic_disable_version_39);
     RefilterSupportedVersions();
   }
diff --git a/quic/core/quic_version_manager.h b/quic/core/quic_version_manager.h
index 4fedae3..db9f2c5 100644
--- a/quic/core/quic_version_manager.h
+++ b/quic/core/quic_version_manager.h
@@ -46,8 +46,6 @@
   bool enable_version_46_;
   // quic_enable_version_44 flag
   bool enable_version_44_;
-  // quic_enable_version_43 flag
-  bool enable_version_43_;
   // quic_disable_version_39 flag
   bool disable_version_39_;
   // The list of versions that may be supported.
diff --git a/quic/core/quic_version_manager_test.cc b/quic/core/quic_version_manager_test.cc
index 7c7a08d..9a7b2a3 100644
--- a/quic/core/quic_version_manager_test.cc
+++ b/quic/core/quic_version_manager_test.cc
@@ -22,20 +22,16 @@
   SetQuicReloadableFlag(quic_enable_version_47, false);
   SetQuicReloadableFlag(quic_enable_version_46, false);
   SetQuicReloadableFlag(quic_enable_version_44, false);
-  SetQuicReloadableFlag(quic_enable_version_43, false);
   SetQuicReloadableFlag(quic_disable_version_39, true);
   QuicVersionManager manager(AllSupportedVersions());
 
   EXPECT_EQ(FilterSupportedTransportVersions(AllSupportedTransportVersions()),
             manager.GetSupportedTransportVersions());
 
-  EXPECT_TRUE(manager.GetSupportedTransportVersions().empty());
-
-  SetQuicReloadableFlag(quic_disable_version_39, false);
-  EXPECT_EQ(QuicTransportVersionVector({QUIC_VERSION_39}),
+  EXPECT_EQ(QuicTransportVersionVector({QUIC_VERSION_43}),
             manager.GetSupportedTransportVersions());
 
-  SetQuicReloadableFlag(quic_enable_version_43, true);
+  SetQuicReloadableFlag(quic_disable_version_39, false);
   EXPECT_EQ(QuicTransportVersionVector({QUIC_VERSION_43, QUIC_VERSION_39}),
             manager.GetSupportedTransportVersions());
 
diff --git a/quic/core/quic_versions.cc b/quic/core/quic_versions.cc
index c4564a7..a27b77c 100644
--- a/quic/core/quic_versions.cc
+++ b/quic/core/quic_versions.cc
@@ -239,30 +239,22 @@
       if (GetQuicReloadableFlag(quic_enable_version_99) &&
           GetQuicReloadableFlag(quic_enable_version_47) &&
           GetQuicReloadableFlag(quic_enable_version_46) &&
-          GetQuicReloadableFlag(quic_enable_version_44) &&
-          GetQuicReloadableFlag(quic_enable_version_43)) {
+          GetQuicReloadableFlag(quic_enable_version_44)) {
         filtered_versions.push_back(version);
       }
     } else if (version.transport_version == QUIC_VERSION_47) {
       if (GetQuicReloadableFlag(quic_enable_version_47) &&
           GetQuicReloadableFlag(quic_enable_version_46) &&
-          GetQuicReloadableFlag(quic_enable_version_44) &&
-          GetQuicReloadableFlag(quic_enable_version_43)) {
+          GetQuicReloadableFlag(quic_enable_version_44)) {
         filtered_versions.push_back(version);
       }
     } else if (version.transport_version == QUIC_VERSION_46) {
       if (GetQuicReloadableFlag(quic_enable_version_46) &&
-          GetQuicReloadableFlag(quic_enable_version_44) &&
-          GetQuicReloadableFlag(quic_enable_version_43)) {
+          GetQuicReloadableFlag(quic_enable_version_44)) {
         filtered_versions.push_back(version);
       }
     } else if (version.transport_version == QUIC_VERSION_44) {
-      if (GetQuicReloadableFlag(quic_enable_version_44) &&
-          GetQuicReloadableFlag(quic_enable_version_43)) {
-        filtered_versions.push_back(version);
-      }
-    } else if (version.transport_version == QUIC_VERSION_43) {
-      if (GetQuicReloadableFlag(quic_enable_version_43)) {
+      if (GetQuicReloadableFlag(quic_enable_version_44)) {
         filtered_versions.push_back(version);
       }
     } else if (version.transport_version == QUIC_VERSION_39) {
@@ -468,9 +460,6 @@
   if (parsed_version.transport_version >= QUIC_VERSION_44) {
     SetQuicReloadableFlag(quic_enable_version_44, true);
   }
-  if (parsed_version.transport_version >= QUIC_VERSION_43) {
-    SetQuicReloadableFlag(quic_enable_version_43, true);
-  }
 }
 
 #undef RETURN_STRING_LITERAL  // undef for jumbo builds
diff --git a/quic/core/quic_versions_test.cc b/quic/core/quic_versions_test.cc
index 51a185f..c19e621 100644
--- a/quic/core/quic_versions_test.cc
+++ b/quic/core/quic_versions_test.cc
@@ -342,7 +342,6 @@
 TEST_F(QuicVersionsTest, FilterSupportedTransportVersionsAllVersions) {
   QuicTransportVersionVector all_versions = AllSupportedTransportVersions();
   SetQuicReloadableFlag(quic_disable_version_39, false);
-  SetQuicReloadableFlag(quic_enable_version_43, true);
   SetQuicReloadableFlag(quic_enable_version_44, true);
   SetQuicReloadableFlag(quic_enable_version_46, true);
   SetQuicReloadableFlag(quic_enable_version_47, true);
@@ -367,7 +366,6 @@
 TEST_F(QuicVersionsTest, FilterSupportedTransportVersionsNo99) {
   QuicTransportVersionVector all_versions = AllSupportedTransportVersions();
   SetQuicReloadableFlag(quic_disable_version_39, false);
-  SetQuicReloadableFlag(quic_enable_version_43, true);
   SetQuicReloadableFlag(quic_enable_version_44, true);
   SetQuicReloadableFlag(quic_enable_version_46, true);
   SetQuicReloadableFlag(quic_enable_version_47, true);
@@ -392,7 +390,6 @@
 TEST_F(QuicVersionsTest, FilterSupportedTransportVersionsNo47) {
   QuicTransportVersionVector all_versions = AllSupportedTransportVersions();
   SetQuicReloadableFlag(quic_disable_version_39, false);
-  SetQuicReloadableFlag(quic_enable_version_43, true);
   SetQuicReloadableFlag(quic_enable_version_44, true);
   SetQuicReloadableFlag(quic_enable_version_46, true);
   SetQuicReloadableFlag(quic_enable_version_47, false);
@@ -416,7 +413,6 @@
 TEST_F(QuicVersionsTest, FilterSupportedTransportVersionsNo46) {
   QuicTransportVersionVector all_versions = AllSupportedTransportVersions();
   SetQuicReloadableFlag(quic_disable_version_39, false);
-  SetQuicReloadableFlag(quic_enable_version_43, true);
   SetQuicReloadableFlag(quic_enable_version_44, true);
   SetQuicReloadableFlag(quic_enable_version_46, false);
   SetQuicReloadableFlag(quic_enable_version_47, false);
@@ -440,7 +436,6 @@
 TEST_F(QuicVersionsTest, FilterSupportedTransportVersionsNo44) {
   QuicTransportVersionVector all_versions = AllSupportedTransportVersions();
   SetQuicReloadableFlag(quic_disable_version_39, false);
-  SetQuicReloadableFlag(quic_enable_version_43, true);
   SetQuicReloadableFlag(quic_enable_version_44, false);
   SetQuicReloadableFlag(quic_enable_version_46, false);
   SetQuicReloadableFlag(quic_enable_version_47, false);
@@ -461,33 +456,9 @@
   ASSERT_EQ(expected_parsed_versions, FilterSupportedVersions(parsed_versions));
 }
 
-TEST_F(QuicVersionsTest, FilterSupportedTransportVersionsNo43) {
-  QuicTransportVersionVector all_versions = AllSupportedTransportVersions();
-  SetQuicReloadableFlag(quic_disable_version_39, false);
-  SetQuicReloadableFlag(quic_enable_version_43, false);
-  SetQuicReloadableFlag(quic_enable_version_44, false);
-  SetQuicReloadableFlag(quic_enable_version_46, false);
-  SetQuicReloadableFlag(quic_enable_version_47, false);
-  SetQuicReloadableFlag(quic_enable_version_99, false);
-  ParsedQuicVersionVector parsed_versions;
-  for (QuicTransportVersion version : all_versions) {
-    parsed_versions.push_back(ParsedQuicVersion(PROTOCOL_QUIC_CRYPTO, version));
-  }
-  QuicTransportVersionVector expected_versions = {QUIC_VERSION_39};
-  ParsedQuicVersionVector expected_parsed_versions;
-  for (QuicTransportVersion version : expected_versions) {
-    expected_parsed_versions.push_back(
-        ParsedQuicVersion(PROTOCOL_QUIC_CRYPTO, version));
-  }
-
-  ASSERT_EQ(expected_versions, FilterSupportedTransportVersions(all_versions));
-  ASSERT_EQ(expected_parsed_versions, FilterSupportedVersions(parsed_versions));
-}
-
 TEST_F(QuicVersionsTest, FilterSupportedTransportVersionsNo39) {
   QuicTransportVersionVector all_versions = AllSupportedTransportVersions();
   SetQuicReloadableFlag(quic_disable_version_39, true);
-  SetQuicReloadableFlag(quic_enable_version_43, true);
   SetQuicReloadableFlag(quic_enable_version_44, false);
   SetQuicReloadableFlag(quic_enable_version_46, false);
   SetQuicReloadableFlag(quic_enable_version_47, false);
@@ -608,7 +579,6 @@
       ParsedQuicVersion(PROTOCOL_TLS1_3, QUIC_VERSION_99);
   SetQuicFlag(FLAGS_quic_supports_tls_handshake, false);
   SetQuicReloadableFlag(quic_disable_version_39, false);
-  SetQuicReloadableFlag(quic_enable_version_43, true);
   SetQuicReloadableFlag(quic_enable_version_44, true);
   SetQuicReloadableFlag(quic_enable_version_46, true);
   SetQuicReloadableFlag(quic_enable_version_47, false);
diff --git a/quic/quartc/quartc_endpoint_test.cc b/quic/quartc/quartc_endpoint_test.cc
index 5af7c87..567ccdd 100644
--- a/quic/quartc/quartc_endpoint_test.cc
+++ b/quic/quartc/quartc_endpoint_test.cc
@@ -88,7 +88,6 @@
   // matter, but they must be enabled so that the version manager doesn't filter
   // them out.
   SetQuicReloadableFlag(quic_enable_version_46, true);
-  SetQuicReloadableFlag(quic_enable_version_43, true);
 
   // Reset the client endpoint to prefer version 46 but also be capable of
   // speaking version 43.
@@ -135,7 +134,6 @@
   // matter, but they must be enabled so that the version manager doesn't filter
   // them out.
   SetQuicReloadableFlag(quic_enable_version_46, true);
-  SetQuicReloadableFlag(quic_enable_version_43, true);
 
   // Reset the client endpoint to only speak version 43.
   ParsedQuicVersionVector client_versions;
@@ -182,7 +180,6 @@
   // matter, but they must be enabled so that the version manager doesn't filter
   // them out.
   SetQuicReloadableFlag(quic_enable_version_46, true);
-  SetQuicReloadableFlag(quic_enable_version_43, true);
 
   // Reset the client endpoint to only speak version 43.
   ParsedQuicVersionVector client_versions;