You invaded the conversation.

[beachboy]

If you see two people talking, approach them, and start talking to them without asking their permission, can I say you "invaded" the conversation? Is there a more natural way to say it?

 

[tedmc]

intrude into the conversation

 

[5jj]

You interrupted or broke into their conversation,

 

[Rover_KE]

You butted in.

 

[Skrej]

I have to say, although the original is not natural, I do like it. It's a perfect description, and should become a commonly used phrase.

I have definitely had private conversations that felt like they were invaded by unwanted participants.

 

[Tarheel]

It depends, I think, on how well you know the interrupter. If a perfect stranger butts in that's one thing. If it's a close friend that's something else.