Charlize Theron & Sean Penn ... THEY'RE DONE

One of Hollywood's top "Really? They're a Couple?" couples is no longer ... Charlize Theron and Sean Penn have parted ways.

They'd been together since 2013 and got engaged in December 2014. Charlize and Sean had been friends for years before hooking up.

Theron was the one who broke things off ... so says Us Weekly.

They were extremely tight ... each having the other's back when stories surfaced about them individually or as a couple.

They were last spotted together last month in Austria.