New York Knicks fans celebrated like they won the NBA Finals after their beloved team advanced to the second round of the playoffs on Wednesday ... and they made it clear how they felt about their next opponent as they partied in the streets.

The Knicks made it to the semifinals after beating Donovan Mitchell and the Cavaliers to complete their first-round series in five games ... and their loyal fan base let their emotions loose right near Madison Square Garden.

The whole bash was caught on video ... and you can see a ton of fans in orange and blue jumping up and down shortly after the final buzzer rang.

The hyped-up crowd chanted many things, including "F*** Miami" ... and even Trae Young, a longtime nemesis of the Knicks fandom, caught a few strays.

Fans even booed a Heat supporter, who happened to be in the crowd wearing a Jimmy Butler jersey ... and former Knicks president Phil Jackson also got thrown into the chants as folks reminisced over his bad tenure with the team.

People even treated the victory like Warped Tour ... as one fan jumped on top of Knicks fans and started crowd surfing.

The fans have every reason to celebrate -- it's the first time in 10 years the Knicks made it to the second round ... and there's a bit of history between NY and Miami going back to the '90s.