NBA's Jeff Adrien: Charged with Felony ... In Alleged Valet Car Theft

The ex-NBA player who allegedly jacked a car from a hotel valet in Hollywood and then went on a joyride has been charged with a felony ... TMZ Sports has learned.

We broke the story ... Jeff Adrien was arrested for allegedly taking a sweet 2015 Mercedes S550 from a hotel valet on Dec. 7th without permission from the actual owner.

Adrien allegedly drove the car around town ... before eventually returning it to the hotel. He was arrested a short time later when the owner discovered what happened.

Adrien's rep had previously told us the whole thing was a giant misunderstanding and it would all be cleared up.

But now, we've learned that ain't exactly the case ... 'cause prosecutors have hit the 29-year-old with one count of driving or taking a vehicle without consent -- a felony.