By TMZ Sports

Former middleweight champ Jermain Taylor is a wanted man -- TMZ Sports has learned an arrest warrant has been issued after JT allegedly attacked a man at a rehab center.

As for the backstory ... law enforcement sources tell us Taylor allegedly attacked another patient at a rehab facility in Little Rock on May 13th ... knocking the man to the floor.

We're told the alleged victim was transported to a nearby hospital -- and was treated in the intensive care unit.

Taylor has been in rehab on a court order since March following a string of disturbing incidents -- including an altercation at a parade where Taylor allegedly pulled a gun on a family and another incident where he shot his cousin.

Taylor's attorney Christian Alexander says he believes the complaint is "frivolous" -- and says he's already spoken with witnesses who believe the whole thing is a shameless attempt to shake down a famous athlete.

The legal issues forced the IBF to strip Taylor of his newly won middleweight title several months ago. The belt is being contested n June 20th between David Lemieux and Hassan N'Dam. 

Story developing ...