Blueface's GF Chrisean Punches Him in Arizona Bar, Gets Arrested

Blueface's girlfriend is in police custody after punching him square in the face -- the second time in less than a month -- but he's begging cops to let her go free.

Chrisean Rock unloaded on the rapper Sunday night while they were in Whiskey Row bar in Scottsdale, AZ. Blueface was standing in front of Chrisean when she hauled back and struck him twice in the face.

She landed both shots, sending Blueface backward and he made no attempt to go back at her. Instead, security took her down ... pinning Chrisean to the ground until Scottsdale PD arrived to haul her off in handcuffs.

So, Blueface's reaction to the violent incident? "Free Rock!!!"

He posted a video saying, "We don't ever make the same mistake twice" ... clearly referring to their very public fight earlier this month.

TMZ broke the story when they both went at each other on the streets of Hollywood -- Chrisean threw the first punch, but Blueface, who's slated to box Nick Young in a celeb event next month, fought back, pinning her to the ground. Cops didn't witness the fight, but after seeing video said they'd opened an investigation.

Nothing's come of that incident yet, and the couple never broke up over it, but now -- with Chrisean in jail -- Blueface says he wants her freed, we think. He was kinda laughing during the video.

One thing he didn't laugh about was the punch, as he put it ... "She hit me with a banger. I was like, oooh!!!"