Katt Williams is in custody again -- cops scooped him up Wednesday for that brawl with a 17-year-old.
Gainesville PD in Georgia tell TMZ ... officers showed up at Katt's house and arrested him. As we told you, an arrest warrant was issued on Monday. Katt was booked around 2:30 PM, and will be held until his court appearance Thursday.
You'll remember ... Williams was seen in a video last week punching 17-year-old Luke Wash after a soccer game. Both Katt and Wash were charged with disorderly conduct.
Luke turned himself in on Monday.