MYSTIKAL REPORTS TO JAIL!

Rapper Mystikal -- famous for his 2000 hit "Shake Ya Ass" -- just checked into a Louisiana jail this morning, where he's expected to serve out the rest of a 90-day sentence for domestic abuse.

Mystikal -- real name Michael Tyler -- was arrested in Baton Rouge on a domestic abuse charge back in February, and a judge ruled it was a violation of his probation. The circumstances surrounding the arrest are unclear.

Mystikal was put on 5-year probation following a 6-year prison stint for sexual battery and extortion.

Mystikal pled guilty in 2003 to forcing his hairstylist to perform oral sex on him.

The judge has already given Mystikal credit for 9 days served while he was detained following his February arrest. He has 81 days left. SOURCE