diff --git a/CHANGES.txt b/CHANGES.txt
index 9ac2873c29..7682fbdd19 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -2,6 +2,17 @@ Unreleased Changes (C++/Java/Python/PHP/Objective-C/C#/Ruby/JavaScript)
   Protocol Compiler
   * Make proto2::Message::DiscardUnknownFields() non-virtual
 
+2021-10-04 version 3.18.1 (C++/Java/Python/PHP/Objective-C/C#/Ruby/JavaScript)
+
+  Python
+  * Update setup.py to reflect that we now require at least Python 3.5 (#8989)
+  * Performance fix for DynamicMessage: force GetRaw() to be inlined (#9023)
+
+  Ruby
+  * Update ruby_generator.cc to allow proto2 imports in proto3 (#9003)
+
+2021-09-13 version 3.18.0 (C++/Java/Python/PHP/Objective-C/C#/Ruby/JavaScript)
+
   Python
   * Removed Python 2.x support.
   * Pure python descriptor_pool.AddSerializedFile() will always build the
diff --git a/Protobuf-C++.podspec b/Protobuf-C++.podspec
index 4a524e68d7..f285e58af8 100644
--- a/Protobuf-C++.podspec
+++ b/Protobuf-C++.podspec
@@ -1,6 +1,6 @@
 Pod::Spec.new do |s|
   s.name     = 'Protobuf-C++'
-  s.version  = '3.18.0'
+  s.version  = '3.18.1'
   s.summary  = 'Protocol Buffers v3 runtime library for C++.'
   s.homepage = 'https://github.com/google/protobuf'
   s.license  = '3-Clause BSD License'
diff --git a/Protobuf.podspec b/Protobuf.podspec
index a3c4380884..4a5f7dd9c1 100644
--- a/Protobuf.podspec
+++ b/Protobuf.podspec
@@ -5,7 +5,7 @@
 # dependent projects use the :git notation to refer to the library.
 Pod::Spec.new do |s|
   s.name     = 'Protobuf'
-  s.version  = '3.18.0'
+  s.version  = '3.18.1'
   s.summary  = 'Protocol Buffers v.3 runtime library for Objective-C.'
   s.homepage = 'https://github.com/protocolbuffers/protobuf'
   s.license  = '3-Clause BSD License'
diff --git a/configure.ac b/configure.ac
index 829568f76d..b7466c28b5 100644
--- a/configure.ac
+++ b/configure.ac
@@ -17,7 +17,7 @@ AC_PREREQ(2.59)
 # In the SVN trunk, the version should always be the next anticipated release
 # version with the "-pre" suffix.  (We used to use "-SNAPSHOT" but this pushed
 # the size of one file name in the dist tarfile over the 99-char limit.)
-AC_INIT([Protocol Buffers],[3.18.0],[protobuf@googlegroups.com],[protobuf])
+AC_INIT([Protocol Buffers],[3.18.1],[protobuf@googlegroups.com],[protobuf])
 
 AM_MAINTAINER_MODE([enable])
 
diff --git a/csharp/Google.Protobuf.Tools.nuspec b/csharp/Google.Protobuf.Tools.nuspec
index 11b6618abe..8e5786fdbd 100644
--- a/csharp/Google.Protobuf.Tools.nuspec
+++ b/csharp/Google.Protobuf.Tools.nuspec
@@ -5,7 +5,7 @@
     <title>Google Protocol Buffers tools</title>
     <summary>Tools for Protocol Buffers - Google's data interchange format.</summary>
     <description>See project site for more info.</description>
-    <version>3.18.0</version>
+    <version>3.18.1</version>
     <authors>Google Inc.</authors>
     <owners>protobuf-packages</owners>
     <licenseUrl>https://github.com/protocolbuffers/protobuf/blob/master/LICENSE</licenseUrl>
diff --git a/csharp/src/Google.Protobuf/Google.Protobuf.csproj b/csharp/src/Google.Protobuf/Google.Protobuf.csproj
index c5996a5dfe..f6d6069102 100644
--- a/csharp/src/Google.Protobuf/Google.Protobuf.csproj
+++ b/csharp/src/Google.Protobuf/Google.Protobuf.csproj
@@ -4,7 +4,7 @@
     <Description>C# runtime library for Protocol Buffers - Google's data interchange format.</Description>
     <Copyright>Copyright 2015, Google Inc.</Copyright>
     <AssemblyTitle>Google Protocol Buffers</AssemblyTitle>
-    <VersionPrefix>3.18.0</VersionPrefix>
+    <VersionPrefix>3.18.1</VersionPrefix>
     <!-- C# 7.2 is required for Span/BufferWriter/ReadOnlySequence -->
     <LangVersion>7.2</LangVersion>
     <Authors>Google Inc.</Authors>
diff --git a/java/bom/pom.xml b/java/bom/pom.xml
index 6b624ec993..c4ec685537 100644
--- a/java/bom/pom.xml
+++ b/java/bom/pom.xml
@@ -4,7 +4,7 @@
 
   <groupId>com.google.protobuf</groupId>
   <artifactId>protobuf-bom</artifactId>
-  <version>3.18.0</version>
+  <version>3.18.1</version>
   <packaging>pom</packaging>
 
   <name>Protocol Buffers [BOM]</name>
diff --git a/java/core/pom.xml b/java/core/pom.xml
index bf185b0564..838f4a7131 100644
--- a/java/core/pom.xml
+++ b/java/core/pom.xml
@@ -4,7 +4,7 @@
   <parent>
     <groupId>com.google.protobuf</groupId>
     <artifactId>protobuf-parent</artifactId>
-    <version>3.18.0</version>
+    <version>3.18.1</version>
   </parent>
 
   <artifactId>protobuf-java</artifactId>
diff --git a/java/kotlin-lite/pom.xml b/java/kotlin-lite/pom.xml
index d6342ee088..0720766132 100644
--- a/java/kotlin-lite/pom.xml
+++ b/java/kotlin-lite/pom.xml
@@ -4,7 +4,7 @@
   <parent>
     <groupId>com.google.protobuf</groupId>
     <artifactId>protobuf-parent</artifactId>
-    <version>3.18.0</version>
+    <version>3.18.1</version>
   </parent>
 
   <artifactId>protobuf-kotlin-lite</artifactId>
diff --git a/java/kotlin/pom.xml b/java/kotlin/pom.xml
index 263be68d34..ad25304949 100644
--- a/java/kotlin/pom.xml
+++ b/java/kotlin/pom.xml
@@ -4,7 +4,7 @@
   <parent>
     <groupId>com.google.protobuf</groupId>
     <artifactId>protobuf-parent</artifactId>
-    <version>3.18.0</version>
+    <version>3.18.1</version>
   </parent>
 
   <artifactId>protobuf-kotlin</artifactId>
diff --git a/java/lite/pom.xml b/java/lite/pom.xml
index 358ba46aa4..a7bbc966a6 100644
--- a/java/lite/pom.xml
+++ b/java/lite/pom.xml
@@ -4,7 +4,7 @@
   <parent>
     <groupId>com.google.protobuf</groupId>
     <artifactId>protobuf-parent</artifactId>
-    <version>3.18.0</version>
+    <version>3.18.1</version>
   </parent>
 
   <artifactId>protobuf-javalite</artifactId>
diff --git a/java/pom.xml b/java/pom.xml
index d8a4b971e4..650bbcfb2f 100644
--- a/java/pom.xml
+++ b/java/pom.xml
@@ -4,7 +4,7 @@
 
   <groupId>com.google.protobuf</groupId>
   <artifactId>protobuf-parent</artifactId>
-  <version>3.18.0</version>
+  <version>3.18.1</version>
   <packaging>pom</packaging>
 
   <name>Protocol Buffers [Parent]</name>
diff --git a/java/util/pom.xml b/java/util/pom.xml
index 8a8e159ebc..6585307526 100644
--- a/java/util/pom.xml
+++ b/java/util/pom.xml
@@ -4,7 +4,7 @@
   <parent>
     <groupId>com.google.protobuf</groupId>
     <artifactId>protobuf-parent</artifactId>
-    <version>3.18.0</version>
+    <version>3.18.1</version>
   </parent>
 
   <artifactId>protobuf-java-util</artifactId>
diff --git a/js/package.json b/js/package.json
index 10426a3528..33f3009255 100644
--- a/js/package.json
+++ b/js/package.json
@@ -1,6 +1,6 @@
 {
   "name": "google-protobuf",
-  "version": "3.18.0",
+  "version": "3.18.1",
   "description": "Protocol Buffers for JavaScript",
   "main": "google-protobuf.js",
   "files": [
diff --git a/php/ext/google/protobuf/package.xml b/php/ext/google/protobuf/package.xml
index 7cf1a817a8..f083785bb1 100644
--- a/php/ext/google/protobuf/package.xml
+++ b/php/ext/google/protobuf/package.xml
@@ -10,11 +10,11 @@
   <email>protobuf-opensource@google.com</email>
   <active>yes</active>
  </lead>
- <date>2021-09-13</date>
- <time>11:30:58</time>
+ <date>2021-10-04</date>
+ <time>13:03:51</time>
  <version>
-  <release>3.18.0</release>
-  <api>3.18.0</api>
+  <release>3.18.1</release>
+  <api>3.18.1</api>
  </version>
  <stability>
   <release>stable</release>
@@ -22,7 +22,7 @@
  </stability>
  <license uri="https://opensource.org/licenses/BSD-3-Clause">3-Clause BSD License</license>
  <notes>
- * No new changes in 3.18.0
+ * No new changes in 3.18.1
  </notes>
  <contents>
   <dir baseinstalldir="/" name="/">
@@ -1083,5 +1083,20 @@ G  A release.
    <notes>
    </notes>
   </release>
+  <release>
+   <version>
+    <release>3.18.1</release>
+    <api>3.18.1</api>
+   </version>
+   <stability>
+    <release>stable</release>
+    <api>stable</api>
+   </stability>
+   <date>2021-10-04</date>
+   <time>13:03:51</time>
+   <license uri="https://opensource.org/licenses/BSD-3-Clause">3-Clause BSD License</license>
+   <notes>
+   </notes>
+  </release>
  </changelog>
 </package>
diff --git a/php/ext/google/protobuf/protobuf.h b/php/ext/google/protobuf/protobuf.h
index dbebca3883..8b5c8aa857 100644
--- a/php/ext/google/protobuf/protobuf.h
+++ b/php/ext/google/protobuf/protobuf.h
@@ -91,7 +91,7 @@ ZEND_BEGIN_ARG_INFO_EX(arginfo_setter, 0, 0, 1)
   ZEND_ARG_INFO(0, value)
 ZEND_END_ARG_INFO()
 
-#define PHP_PROTOBUF_VERSION "3.18.0"
+#define PHP_PROTOBUF_VERSION "3.18.1"
 
 // ptr -> PHP object cache. This is a weak map that caches lazily-created
 // wrapper objects around upb types:
diff --git a/protobuf_version.bzl b/protobuf_version.bzl
index f3ef08340d..7f6d71460c 100644
--- a/protobuf_version.bzl
+++ b/protobuf_version.bzl
@@ -1 +1 @@
-PROTOBUF_VERSION = '3.18.0'
+PROTOBUF_VERSION = '3.18.1'
diff --git a/protoc-artifacts/pom.xml b/protoc-artifacts/pom.xml
index 93b118baaf..c3aa37771f 100644
--- a/protoc-artifacts/pom.xml
+++ b/protoc-artifacts/pom.xml
@@ -8,7 +8,7 @@
   </parent>
   <groupId>com.google.protobuf</groupId>
   <artifactId>protoc</artifactId>
-  <version>3.18.0</version>
+  <version>3.18.1</version>
   <packaging>pom</packaging>
   <name>Protobuf Compiler</name>
   <description>
diff --git a/python/google/protobuf/__init__.py b/python/google/protobuf/__init__.py
index cb4740412a..b8122e82ae 100644
--- a/python/google/protobuf/__init__.py
+++ b/python/google/protobuf/__init__.py
@@ -30,4 +30,4 @@
 
 # Copyright 2007 Google Inc. All Rights Reserved.
 
-__version__ = '3.18.0'
+__version__ = '3.18.1'
diff --git a/ruby/google-protobuf.gemspec b/ruby/google-protobuf.gemspec
index 3647d8bb6b..7a9e3f38b7 100644
--- a/ruby/google-protobuf.gemspec
+++ b/ruby/google-protobuf.gemspec
@@ -1,6 +1,6 @@
 Gem::Specification.new do |s|
   s.name        = "google-protobuf"
-  s.version     = "3.18.0"
+  s.version     = "3.18.1"
   git_tag       = "v#{s.version.to_s.sub('.rc.', '-rc')}" # Converts X.Y.Z.rc.N to vX.Y.Z-rcN, used for the git tag
   s.licenses    = ["BSD-3-Clause"]
   s.summary     = "Protocol Buffers"
diff --git a/src/Makefile.am b/src/Makefile.am
index ce65d797e7..102af04417 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -18,7 +18,7 @@ else
 PTHREAD_DEF =
 endif
 
-PROTOBUF_VERSION = 29:0:0
+PROTOBUF_VERSION = 29:1:0
 
 if GCC
 # Turn on all warnings except for sign comparison (we ignore sign comparison
diff --git a/src/google/protobuf/any.pb.h b/src/google/protobuf/any.pb.h
index 46c90bdc99..60308ffbaf 100644
--- a/src/google/protobuf/any.pb.h
+++ b/src/google/protobuf/any.pb.h
@@ -13,7 +13,7 @@
 #error incompatible with your Protocol Buffer headers. Please update
 #error your headers.
 #endif
-#if 3018000 < PROTOBUF_MIN_PROTOC_VERSION
+#if 3018001 < PROTOBUF_MIN_PROTOC_VERSION
 #error This file was generated by an older version of protoc which is
 #error incompatible with your Protocol Buffer headers. Please
 #error regenerate this file with a newer version of protoc.
diff --git a/src/google/protobuf/api.pb.h b/src/google/protobuf/api.pb.h
index 84de2cdccc..e614f07a32 100644
--- a/src/google/protobuf/api.pb.h
+++ b/src/google/protobuf/api.pb.h
@@ -13,7 +13,7 @@
 #error incompatible with your Protocol Buffer headers. Please update
 #error your headers.
 #endif
-#if 3018000 < PROTOBUF_MIN_PROTOC_VERSION
+#if 3018001 < PROTOBUF_MIN_PROTOC_VERSION
 #error This file was generated by an older version of protoc which is
 #error incompatible with your Protocol Buffer headers. Please
 #error regenerate this file with a newer version of protoc.
diff --git a/src/google/protobuf/compiler/plugin.pb.h b/src/google/protobuf/compiler/plugin.pb.h
index 20d8169a11..76c3da1de7 100644
--- a/src/google/protobuf/compiler/plugin.pb.h
+++ b/src/google/protobuf/compiler/plugin.pb.h
@@ -13,7 +13,7 @@
 #error incompatible with your Protocol Buffer headers. Please update
 #error your headers.
 #endif
-#if 3018000 < PROTOBUF_MIN_PROTOC_VERSION
+#if 3018001 < PROTOBUF_MIN_PROTOC_VERSION
 #error This file was generated by an older version of protoc which is
 #error incompatible with your Protocol Buffer headers. Please
 #error regenerate this file with a newer version of protoc.
diff --git a/src/google/protobuf/descriptor.pb.h b/src/google/protobuf/descriptor.pb.h
index 9695983303..cf425ff7e4 100644
--- a/src/google/protobuf/descriptor.pb.h
+++ b/src/google/protobuf/descriptor.pb.h
@@ -13,7 +13,7 @@
 #error incompatible with your Protocol Buffer headers. Please update
 #error your headers.
 #endif
-#if 3018000 < PROTOBUF_MIN_PROTOC_VERSION
+#if 3018001 < PROTOBUF_MIN_PROTOC_VERSION
 #error This file was generated by an older version of protoc which is
 #error incompatible with your Protocol Buffer headers. Please
 #error regenerate this file with a newer version of protoc.
diff --git a/src/google/protobuf/duration.pb.h b/src/google/protobuf/duration.pb.h
index cbf346f7bc..292c170750 100644
--- a/src/google/protobuf/duration.pb.h
+++ b/src/google/protobuf/duration.pb.h
@@ -13,7 +13,7 @@
 #error incompatible with your Protocol Buffer headers. Please update
 #error your headers.
 #endif
-#if 3018000 < PROTOBUF_MIN_PROTOC_VERSION
+#if 3018001 < PROTOBUF_MIN_PROTOC_VERSION
 #error This file was generated by an older version of protoc which is
 #error incompatible with your Protocol Buffer headers. Please
 #error regenerate this file with a newer version of protoc.
diff --git a/src/google/protobuf/empty.pb.h b/src/google/protobuf/empty.pb.h
index ae1504452c..000c3dfaad 100644
--- a/src/google/protobuf/empty.pb.h
+++ b/src/google/protobuf/empty.pb.h
@@ -13,7 +13,7 @@
 #error incompatible with your Protocol Buffer headers. Please update
 #error your headers.
 #endif
-#if 3018000 < PROTOBUF_MIN_PROTOC_VERSION
+#if 3018001 < PROTOBUF_MIN_PROTOC_VERSION
 #error This file was generated by an older version of protoc which is
 #error incompatible with your Protocol Buffer headers. Please
 #error regenerate this file with a newer version of protoc.
diff --git a/src/google/protobuf/field_mask.pb.h b/src/google/protobuf/field_mask.pb.h
index fa3b3365dc..b0fb89254e 100644
--- a/src/google/protobuf/field_mask.pb.h
+++ b/src/google/protobuf/field_mask.pb.h
@@ -13,7 +13,7 @@
 #error incompatible with your Protocol Buffer headers. Please update
 #error your headers.
 #endif
-#if 3018000 < PROTOBUF_MIN_PROTOC_VERSION
+#if 3018001 < PROTOBUF_MIN_PROTOC_VERSION
 #error This file was generated by an older version of protoc which is
 #error incompatible with your Protocol Buffer headers. Please
 #error regenerate this file with a newer version of protoc.
diff --git a/src/google/protobuf/port_def.inc b/src/google/protobuf/port_def.inc
index aff8c8f325..b5838c41b3 100644
--- a/src/google/protobuf/port_def.inc
+++ b/src/google/protobuf/port_def.inc
@@ -153,7 +153,7 @@
 #ifdef PROTOBUF_VERSION
 #error PROTOBUF_VERSION was previously defined
 #endif
-#define PROTOBUF_VERSION 3018000
+#define PROTOBUF_VERSION 3018001
 
 #ifdef PROTOBUF_MIN_HEADER_VERSION_FOR_PROTOC
 #error PROTOBUF_MIN_HEADER_VERSION_FOR_PROTOC was previously defined
diff --git a/src/google/protobuf/source_context.pb.h b/src/google/protobuf/source_context.pb.h
index 0543017eae..d6bc1daef0 100644
--- a/src/google/protobuf/source_context.pb.h
+++ b/src/google/protobuf/source_context.pb.h
@@ -13,7 +13,7 @@
 #error incompatible with your Protocol Buffer headers. Please update
 #error your headers.
 #endif
-#if 3018000 < PROTOBUF_MIN_PROTOC_VERSION
+#if 3018001 < PROTOBUF_MIN_PROTOC_VERSION
 #error This file was generated by an older version of protoc which is
 #error incompatible with your Protocol Buffer headers. Please
 #error regenerate this file with a newer version of protoc.
diff --git a/src/google/protobuf/struct.pb.h b/src/google/protobuf/struct.pb.h
index 165a9d9f06..83a9d90824 100644
--- a/src/google/protobuf/struct.pb.h
+++ b/src/google/protobuf/struct.pb.h
@@ -13,7 +13,7 @@
 #error incompatible with your Protocol Buffer headers. Please update
 #error your headers.
 #endif
-#if 3018000 < PROTOBUF_MIN_PROTOC_VERSION
+#if 3018001 < PROTOBUF_MIN_PROTOC_VERSION
 #error This file was generated by an older version of protoc which is
 #error incompatible with your Protocol Buffer headers. Please
 #error regenerate this file with a newer version of protoc.
diff --git a/src/google/protobuf/stubs/common.h b/src/google/protobuf/stubs/common.h
index 3e74713d40..1d25852264 100644
--- a/src/google/protobuf/stubs/common.h
+++ b/src/google/protobuf/stubs/common.h
@@ -82,7 +82,7 @@ namespace internal {
 
 // The current version, represented as a single integer to make comparison
 // easier:  major * 10^6 + minor * 10^3 + micro
-#define GOOGLE_PROTOBUF_VERSION 3018000
+#define GOOGLE_PROTOBUF_VERSION 3018001
 
 // A suffix string for alpha, beta or rc releases. Empty for stable releases.
 #define GOOGLE_PROTOBUF_VERSION_SUFFIX ""
diff --git a/src/google/protobuf/timestamp.pb.h b/src/google/protobuf/timestamp.pb.h
index e4f6b2e3b1..66535fec6d 100644
--- a/src/google/protobuf/timestamp.pb.h
+++ b/src/google/protobuf/timestamp.pb.h
@@ -13,7 +13,7 @@
 #error incompatible with your Protocol Buffer headers. Please update
 #error your headers.
 #endif
-#if 3018000 < PROTOBUF_MIN_PROTOC_VERSION
+#if 3018001 < PROTOBUF_MIN_PROTOC_VERSION
 #error This file was generated by an older version of protoc which is
 #error incompatible with your Protocol Buffer headers. Please
 #error regenerate this file with a newer version of protoc.
diff --git a/src/google/protobuf/type.pb.h b/src/google/protobuf/type.pb.h
index 97fe57bfc3..027982829f 100644
--- a/src/google/protobuf/type.pb.h
+++ b/src/google/protobuf/type.pb.h
@@ -13,7 +13,7 @@
 #error incompatible with your Protocol Buffer headers. Please update
 #error your headers.
 #endif
-#if 3018000 < PROTOBUF_MIN_PROTOC_VERSION
+#if 3018001 < PROTOBUF_MIN_PROTOC_VERSION
 #error This file was generated by an older version of protoc which is
 #error incompatible with your Protocol Buffer headers. Please
 #error regenerate this file with a newer version of protoc.
diff --git a/src/google/protobuf/wrappers.pb.h b/src/google/protobuf/wrappers.pb.h
index 48609b2001..e03527ad75 100644
--- a/src/google/protobuf/wrappers.pb.h
+++ b/src/google/protobuf/wrappers.pb.h
@@ -13,7 +13,7 @@
 #error incompatible with your Protocol Buffer headers. Please update
 #error your headers.
 #endif
-#if 3018000 < PROTOBUF_MIN_PROTOC_VERSION
+#if 3018001 < PROTOBUF_MIN_PROTOC_VERSION
 #error This file was generated by an older version of protoc which is
 #error incompatible with your Protocol Buffer headers. Please
 #error regenerate this file with a newer version of protoc.