Right-click (or long-press on mobile) any conversation thread in your Messages list and select Delete Conversation. A confirmation dialog will appear before the deletion is executed.
What Gets Deleted
Deleting a conversation permanently removes:
All messages in the thread — both yours and the other person's
All shared media — images, files, and generated content
The thread itself — it disappears from your Messages list entirely
Important Warnings
Deletion is permanent and irreversible — there is no recovery option, no trash folder, no undo
The deletion only affects your copy of the conversation. The other person may still have their copy unless they also delete it.
If the other person messages you again after deletion, a brand-new conversation thread is created
Tip If you just want to clean up your inbox without losing messages, consider archiving the conversation instead. Archives are non-destructive and can be unarchived at any time.