diff --git a/WORKSPACE b/WORKSPACE
index 2d73153831..23411bb112 100644
--- a/WORKSPACE
+++ b/WORKSPACE
@@ -42,7 +42,7 @@ git_repository(
 # Protobuf
 git_repository(
     name = "com_google_protobuf",
-    tag = "v21.7",
+    tag = "v21.9",
     remote = "https://github.com/protocolbuffers/protobuf.git",
 )
 # Load common dependencies.
diff --git a/bazel/python_deps.txt b/bazel/python_deps.txt
index a3fc7a35ae..9b524dc091 100644
--- a/bazel/python_deps.txt
+++ b/bazel/python_deps.txt
@@ -1,3 +1,3 @@
 absl-py >= 0.13
 numpy >= 1.13.3
-protobuf >= 4.21.5
+protobuf >= 4.21.9
diff --git a/cmake/dependencies/CMakeLists.txt b/cmake/dependencies/CMakeLists.txt
index 257624e829..dbfebbcdf2 100644
--- a/cmake/dependencies/CMakeLists.txt
+++ b/cmake/dependencies/CMakeLists.txt
@@ -100,9 +100,9 @@ if(BUILD_Protobuf)
   FetchContent_Declare(
     protobuf
     GIT_REPOSITORY "https://github.com/protocolbuffers/protobuf.git"
-    GIT_TAG "v21.5"
+    GIT_TAG "v21.9"
     GIT_SUBMODULES ""
-    PATCH_COMMAND git apply --ignore-whitespace "${CMAKE_CURRENT_LIST_DIR}/../../patches/protobuf-v21.5.patch")
+    PATCH_COMMAND git apply --ignore-whitespace "${CMAKE_CURRENT_LIST_DIR}/../../patches/protobuf-v21.9.patch")
   FetchContent_MakeAvailable(protobuf)
   list(POP_BACK CMAKE_MESSAGE_INDENT)
   message(CHECK_PASS "fetched")
diff --git a/ortools/dotnet/Google.OrTools-full.csproj.in b/ortools/dotnet/Google.OrTools-full.csproj.in
index 9562248be2..b0d77670c1 100644
--- a/ortools/dotnet/Google.OrTools-full.csproj.in
+++ b/ortools/dotnet/Google.OrTools-full.csproj.in
@@ -176,7 +176,7 @@
   </ItemGroup>
 
   <ItemGroup>
-    <PackageReference Include="Google.Protobuf" Version="3.21.5"/>
+    <PackageReference Include="Google.Protobuf" Version="3.21.9"/>
   </ItemGroup>
 
   <!-- Need to add required runtime dependencies so Meta-Project will pull runtime Nuget(s) -->
diff --git a/ortools/dotnet/Google.OrTools-local.csproj.in b/ortools/dotnet/Google.OrTools-local.csproj.in
index 1fafa6a936..86245e012b 100644
--- a/ortools/dotnet/Google.OrTools-local.csproj.in
+++ b/ortools/dotnet/Google.OrTools-local.csproj.in
@@ -164,7 +164,7 @@
   </ItemGroup>
 
   <ItemGroup>
-    <PackageReference Include="Google.Protobuf" Version="3.21.5"/>
+    <PackageReference Include="Google.Protobuf" Version="3.21.9"/>
   </ItemGroup>
 
   <!-- Need to add required runtime dependencies so Meta-Project will pull runtime Nuget(s) -->
diff --git a/ortools/java/pom-full.xml.in b/ortools/java/pom-full.xml.in
index 6a17742442..215cddbaad 100644
--- a/ortools/java/pom-full.xml.in
+++ b/ortools/java/pom-full.xml.in
@@ -109,7 +109,7 @@
   <dependency>
     <groupId>com.google.protobuf</groupId>
     <artifactId>protobuf-java</artifactId>
-    <version>3.21.5</version>
+    <version>3.21.9</version>
   </dependency>
 </dependencies>
 
diff --git a/ortools/java/pom-local.xml.in b/ortools/java/pom-local.xml.in
index ea3f98dfc6..a430d178b1 100644
--- a/ortools/java/pom-local.xml.in
+++ b/ortools/java/pom-local.xml.in
@@ -81,7 +81,7 @@
   <dependency>
     <groupId>com.google.protobuf</groupId>
     <artifactId>protobuf-java</artifactId>
-    <version>3.21.5</version>
+    <version>3.21.9</version>
   </dependency>
 </dependencies>
 
diff --git a/ortools/java/pom.xml.in b/ortools/java/pom.xml.in
index b2b3e5e0e7..48ca443158 100644
--- a/ortools/java/pom.xml.in
+++ b/ortools/java/pom.xml.in
@@ -69,7 +69,7 @@
   <dependency>
     <groupId>com.google.protobuf</groupId>
     <artifactId>protobuf-java</artifactId>
-    <version>3.21.5</version>
+    <version>3.21.9</version>
   </dependency>
   <dependency>
     <groupId>junit</groupId>
diff --git a/ortools/python/setup.py.in b/ortools/python/setup.py.in
index c4c521ab6f..307afcf36d 100644
--- a/ortools/python/setup.py.in
+++ b/ortools/python/setup.py.in
@@ -45,7 +45,7 @@ setup(
     install_requires=[
         'absl-py >= 0.13',
         'numpy >= 1.13.3',
-        'protobuf >= 4.21.5',
+        'protobuf >= 4.21.9',
     ],
     package_data={
         '@PYTHON_PROJECT@':[$<$<STREQUAL:$<TARGET_PROPERTY:@PROJECT_NAME@,TYPE>,SHARED_LIBRARY>:'.libs/*','../$<TARGET_SONAME_FILE_NAME:@PROJECT_NAME@>'>],
diff --git a/patches/protobuf-v21.5.patch b/patches/protobuf-v21.9.patch
similarity index 100%
rename from patches/protobuf-v21.5.patch
rename to patches/protobuf-v21.9.patch