diff --git a/docs/upgrade-guides/2-3-0-to-2-4-0.md b/docs/upgrade-guides/2-3-0-to-2-4-0.md
new file mode 100644
index 0000000..c975950
--- /dev/null
+++ b/docs/upgrade-guides/2-3-0-to-2-4-0.md
@@ -0,0 +1,12 @@
+# 2.3.0 to 2.4.0
+
+This document describes the upgrade instructions from `2.3.0` to `2.4.0`.
+
+## Updated Java Version to Java 21
+
+Mission model upgrade steps
+
+- Update Gradle wrapper to one that supports Java 21, Gradle 8.6 is known to work
+- Update the Java sourceCompatibilty/targetCompatability statements in your gradle file (e.g. gov.nasa.jpl.europa.clipper.aerie.adaptations.java-common-conventions.gradle)
+
+Aerie running under JRE 21 can support mission models built with prior JDKs and models built under both JDK 19 and 21 were tested and run as expected
diff --git a/sidebars.js b/sidebars.js
index 14c78ed..a7cc16f 100644
--- a/sidebars.js
+++ b/sidebars.js
@@ -323,6 +323,7 @@ const sidebars = {
     'glossary',
   ],
   upgradeGuides: [
+    'upgrade-guides/2-3-0-to-2-4-0',
     'upgrade-guides/2-2-0-to-2-3-0',
     'upgrade-guides/2-1-0-to-2-2-0',
     'upgrade-guides/2-0-0-to-2-1-0',