The senseless violence, which was caught on video by a horrified onlooker, reportedly began when one woman asked another if the singer Kehlani was still on stage.
She replied 'very rudely' and called her a 'b****', a witness claimed, kicking off seven minutes of savage fighting during the Sunday event.
Navdeep Thind, a Diablo Valley College student who filmed the rampage, said: 'It got kind of brutal. People were saying it was like some WWE stuff, and it really was.
He added, according to SFGate: 'You saw some heads hitting the cement.'
Thind uploaded the video to Twitter, where it went viral.
Comment: You'll want to turn down the volume. There's some horrific 'music' in it, apparently being blasted out at the gathering...
He explained how he believed the brawl began: 'I guess one girl asked the other girl if Kehlani was performing. And I guess the other girl said, "Yeah, she is," but I guess she said it very rudely or angrily, and called her a b****.
'That triggered the other girl to say something like, "Did you just call me a b****?" And that started their argument.'
Despite the gruesome violence of the fighting, police said no arrests were made and had no comment to make.
Thind added: 'It was like a rumble. Like things you see in the movies. It was very intense in person.'
Kehlani wrote on Twitter afterwards that the Pride event was 'rude all day', adding: 'Didn't expect any of this. Don't want to cause a situation because I really care about this community but stay away from Pride if your heart isn't in it.
'San Francisco deserved better today. & the cops are out fully strapped.'
Comment: No, San Francisco deserves precisely what it's got.