UFC's Khabib Nurmagomedov Hospitalized ... OUT OF UFC 209

UFC rising star Khabib Nurmagomedov was hospitalized Thursday evening and will NOT fight at UFC 209.

UFC officials say Khabib was hospitalized for "weight management issues." Khabib was treated and has been released.

Khabib was scheduled to fight Tony Ferguson on Saturday for the interim 155 pound title -- and Dana White had told us the winner would most likely face Conor McGregor.

But now, with Khabib out ... it's unclear what will happen next.