diff --git a/README.md b/README.md
index 9497c43..fa17c5d 100644
--- a/README.md
+++ b/README.md
@@ -25,7 +25,7 @@ must be configured. The following actions are supported:
 - Remove labels
 - Close threads
 - Reopen threads
-- Lock threads with an optional lock reason
+- Lock threads
 - Unlock threads
 
 ## Usage
@@ -80,6 +80,10 @@ pull requests or discussions by grouping them under the
   - Close threads, value must be either `true` or `false`,
     ignored for discussions
   - Optional, defaults to `false`
+- **`close-reason`**
+  - Reason for closing threads, value must be
+    either `completed` or `not planned`, ignored for discussions
+  - Optional, defaults to `completed`
 - **`reopen`**
   - Reopen threads, value must be either `true` or `false`,
     ignored for discussions
@@ -235,6 +239,8 @@ feature:
       :wave: @{issue-author}, please use our idea board to request new features.
     # Close the issue
     close: true
+    # Set a close reason
+    close-reason: 'not planned'
 
 # The `wip` label is added to pull requests
 wip:
diff --git a/src/index.js b/src/index.js
index b5fb23b..7010077 100644
--- a/src/index.js
+++ b/src/index.js
@@ -212,17 +212,24 @@ class App {
         !threadData.merged
       ) {
         core.debug('Reopening');
+
         await this.client.rest.issues.update({...issue, state: 'open'});
       }
 
       if (actions.close && threadData.state === 'open') {
         core.debug('Closing');
-        await this.client.rest.issues.update({...issue, state: 'closed'});
+
+        await this.client.rest.issues.update({
+          ...issue,
+          state: 'closed',
+          state_reason: actions['close-reason']
+        });
       }
     }
 
     if (actions.lock && !threadData.locked) {
       core.debug('Locking');
+
       if (threadType === 'discussion') {
         await this.client.graphql(lockLockableQuery, {
           lockableId: discussion.node_id
@@ -241,6 +248,7 @@ class App {
 
     if (actions.unlock && threadData.locked) {
       core.debug('Unlocking');
+
       if (threadType === 'discussion') {
         await this.client.graphql(unlockLockableQuery, {
           lockableId: discussion.node_id
diff --git a/src/schema.js b/src/schema.js
index d4f2bf5..834d4f6 100644
--- a/src/schema.js
+++ b/src/schema.js
@@ -22,6 +22,22 @@ const extendedJoi = Joi.extend(joi => {
             .filter(Boolean);
         }
 
+        return {value};
+      }
+    }
+  };
+}).extend(joi => {
+  return {
+    type: 'closeReason',
+    base: joi.string(),
+    coerce: {
+      from: 'string',
+      method(value, helpers) {
+        value = value.trim();
+        if (value === 'not planned') {
+          value = 'not_planned';
+        }
+
         return {value};
       }
     }
@@ -50,6 +66,8 @@ const configSchema = Joi.object({
 const actions = {
   close: Joi.boolean(),
 
+  'close-reason': extendedJoi.closeReason().valid('completed', 'not_planned'),
+
   reopen: Joi.boolean(),
 
   lock: Joi.boolean(),
@@ -95,6 +113,7 @@ const actionSchema = Joi.object()
     Joi.string().trim().max(51),
     Joi.object().keys({
       close: actions.close.default(false),
+      'close-reason': actions['close-reason'].default('completed'),
       reopen: actions.reopen.default(false),
       lock: actions.lock.default(false),
       unlock: actions.unlock.default(false),