Six people were hauled off in cuffs when celebratory madness erupted outside Madison Square Garden as the Knicks clinched the NBA finals for the first time in 27 years. 

The raucous crew — among thousands of Knicks diehards who partied like it was 1999 outside The Mecca Monday night — allegedly climbed on light posts and other structures, blocked cars, jumped over police barriers and refused to disperse, law enforcement sources said. 

They were issued summonses for disorderly conduct and processed at the NYPD’s Midtown South Precinct, authorities said. 

Video from the jubilant scene showed one reveler — who appeared no older than his early teens — hoisting himself up a light pole, before two cops immediately slapped cuffs on him when he jumped down.

The crowd of partying fans then erupted into jeers of “Let him free!” and “Boo!

Another video showed people standing on the iconic arena’s marquee, and the outdoor lit-up signs, as one bystander yelled, “You’re going to jail.” 

But an unfazed member of Knicks nation relished the joyful mood – as the hometown team bludgeoned the Cleveland Cavaliers 130-93 at Rocket Arena, punching their ticket to the championship. 

“This is amazing! I waited years for this. I love Jalen Brunson,” he gushed, referring to the Knicks’ guard who was unanimously named the series MVP.

The mob of revelers descended on the Garden despite the NYPD’s move to call off the venue’s usual outdoor watch party during Monday’s playoff game because unruly fans had been clogging the sidewalks during the team’s historic run. 

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 cops reportedly refusing to participate unless fans tone it down a notch. 

“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 Friday.

“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.

No one was taken into custody outside Radio City Music Hall, which remained under control as orange-and-blue clad fans gathered there Monday night for a watch party, cops said.