Rihanna -- Burning Up After Chris Brown Split

Rihanna's gone up in smoke after calling it quits with Chris Brown ... ripping a fat blunt inside a Hollywood nightclub early Monday morning ... and TMZ has the pic.

Sources inside Greystone Manor nightclub tell us, Rihanna arrived around 1am with her assistant and security guard ... and pretty much kept to herself. She left an hour or so later.

As we reported, Rihanna and Chris Brown are officially broken up ... but our sources say it's nothing new for the on-again-off-again couple. We're told they'll be back together in no time.

You might call it a chronic problem.