The red-hot Knicks just suffered their first loss in a while.

Madison Square Garden has been barred from holding its usual outdoor watch party during Monday’s NBA playoff game because the NYPD has had enough of unruly Knicks fans mobbing the city sidewalks and causing trouble, according to cops and sources.

MSG’s permits for the Eastern Conference Finals Game 4 shindig were summarily denied by the city’s Street Activity Permit Office, sources with knowledge of the situation told The Post, with irate police officers reportedly refusing to participate unless fans can get a grip on themselves.

“Games 1 and 2 have seen progressively more problematic issues at the watch parties outside MSG — six arrests last night alone — so the NYPD will not support more watch parties outside the stadium,” a police department spokesperson confirmed.

“But we will continue to review requests to support parties at alternate sites, like Summer Stage,” the spokesperson added, referring to Central Park’s outdoor amphitheater.

The Midtown arena has broadcast Knicks games on massive outdoor screens as the city’s home basketball team battled its way through the playoffs this month, with attendees paying a roughly $10 ticket to enter a cordoned off party area.

But behavior among the crowds gathered on the sidewalks nearby have grown increasingly debauched amid the spectacle.

Pushing, shouting and all-out brawls have cropped up, while frightening scenes of shoving crowds mobbing the sidewalks have circulated online.

As many as 6,000 people have congregated around the parties, with many seen jumping police barriers, drinking in the streets, blocking traffic and drinking in the streets.

Despite Monday’s cancellation, Saturday’s game 3 party — where proceeds will benefit charity — is still on.

The party problems come just weeks after Mayor Mamdani announced the city would have free viewing parties when the soccer World Cup comes to New Jersey across June and July.

Those parties will be held in open outdoor spaces like the Rockefeller Center, the National Tennis Center in Queens, Bronx Terminal Market and Brooklyn Bridge Park.

Madison Square Park declined to comment on its permit problems.