diff --git a/.github/workflows/test-old-branches.yml b/.github/workflows/test-old-branches.yml
index a7dc0210f5..aeb967743a 100644
--- a/.github/workflows/test-old-branches.yml
+++ b/.github/workflows/test-old-branches.yml
@@ -17,7 +17,7 @@ on:
 permissions: {}
 
 env:
-  CURRENTLY_SUPPORTED_BRANCH: '6.4'
+  CURRENTLY_SUPPORTED_BRANCH: '6.5'
 
 jobs:
   dispatch-workflows-for-old-branches:
@@ -37,12 +37,14 @@ jobs:
             'test-npm.yml'
         ]
         branch: [
-            '6.4', '6.3', '6.2', '6.1','6.0',
+            '6.5', '6.4', '6.3', '6.2', '6.1','6.0',
             '5.9', '5.8', '5.7', '5.6', '5.5', '5.4', '5.3', '5.2', '5.1', '5.0',
             '4.9', '4.8', '4.7', '4.6', '4.5', '4.4', '4.3', '4.2', '4.1'
         ]
         include:
           # PHP Compatibility testing was introduced in 5.5.
+          - branch: '6.5'
+            workflow: 'php-compatibility.yml'
           - branch: '6.4'
             workflow: 'php-compatibility.yml'
           - branch: '6.3'
@@ -67,6 +69,8 @@ jobs:
           # End-to-end testing was introduced in 5.3 but was later removed as there were no meaningful assertions.
           # Starting in 5.8 with #52905, some additional tests with real assertions were introduced.
           # Branches 5.8 and newer should be tested to confirm no regressions are introduced.
+          - branch: '6.5'
+            workflow: 'end-to-end-tests.yml'
           - branch: '6.4'
             workflow: 'end-to-end-tests.yml'
           - branch: '6.3'
@@ -83,6 +87,8 @@ jobs:
             workflow: 'end-to-end-tests.yml'
 
           # Performance testing was introduced in 6.2.
+          - branch: '6.5'
+            workflow: 'performance.yml'
           - branch: '6.4'
             workflow: 'performance.yml'
           - branch: '6.3'
diff --git a/SECURITY.md b/SECURITY.md
index 39be6abebf..40fd5039e5 100644
--- a/SECURITY.md
+++ b/SECURITY.md
@@ -10,6 +10,7 @@ Full details of the WordPress Security Policy and the list of covered projects a
 
 | Version | Supported |
 |---------| --------- |
+| 6.5.x   | Yes       |
 | 6.4.x   | Yes       |
 | 6.3.x   | Yes       |
 | 6.2.x   | Yes       |
diff --git a/package-lock.json b/package-lock.json
index 2b7e82118c..053e087738 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,6 +1,6 @@
 {
 	"name": "WordPress",
-	"version": "6.5.0",
+	"version": "6.6.0",
 	"lockfileVersion": 2,
 	"requires": true,
 	"packages": {
diff --git a/package.json b/package.json
index 273b44b865..a7d1cfa067 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
 	"name": "WordPress",
-	"version": "6.5.0",
+	"version": "6.6.0",
 	"description": "WordPress is open source software you can use to create a beautiful website, blog, or app.",
 	"repository": {
 		"type": "svn",
diff --git a/src/wp-includes/version.php b/src/wp-includes/version.php
index ecba13a593..5714742e9d 100644
--- a/src/wp-includes/version.php
+++ b/src/wp-includes/version.php
@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.5-RC1-57778-src';
+$wp_version = '6.6-alpha-57778-src';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.