Open Messenger
Open the chat with the person you want to remove
Tap the person’s name or the chat info icon at the top
Tap Privacy and support or People, depending on your version
Select Block if you want to stop them from contacting you
Select Remove from group if you are removing them from a group chat
If needed, open Facebook and remove them from your friends list to stop Messenger access through friendship
To delete the conversation, go back to the chat list
Swipe left on the chat or press and hold it
Tap Delete
Confirm the deletion