The Knicks have turned the Big Apple into the Big Party.

The NBA champs sent thousands into the streets after knocking off the San Antonio Spurs on Saturday night, with everyone from MTA bus drivers to city firefighters joining the frenzy — while massive crowds sang along to Sinatra’s “New York, New York” in one monster celebration.

And that party’s just starting.

“I think it’s unmatchable,” West Village actor Katya Ferrer told The Post Sunday. “I saw someone today say it’s like a reverse 9/11. I’ve been in New York for 13 years and that collective experience is the closest thing to world peace I’ve ever experienced.

“It’s unifying the city,” she said. “It’s unifying the world. Everyone watched. Everyone was rooting for us.”

Now on tap is a ticker-tape parade down the Canyon of Heroes, city officials announced.

“It’s like a collective effervescence,” said Happy David, who does social media for Casa Magazines. “Everyone is in a great mood. Everyone complimenting each other on their merch.

“Everybody is in a celebratory mood,” she said. “It’s a gift to the neighborhood.”

The party started the second the Knicks pulled off a 94-90 win over the hated Spurs in San Antonio, with cheers erupting from watch parties — big and small — throughout the New York metro area and thousands upon thousands of fans taking to the streets to celebrate.

Knicks fans even took over the Frost Bank Center, the Spurs home court in San Antonio, turning the rival’s arena into a New York shindig.

It’s the first NBA title for the Knicks since 1973, and follows near misses in 1994 and 1999.

While New York sports fan bases are split in baseball, football and hockey loyalty, the Knicks stand alone as the city’s team, with the Nets still not gaining major traction despite their 2012 move to Brooklyn.

“Don’t forget, the Knicks have no competition,” one retired cop said. “The Yankees had the Mets. The Giants had the Jets. The Rangers had the Devils and the Islanders – everyone is a Knick fan.”

Even the less-traveled Westchester County Airport couldn’t escape Knicks fever, with dozens of frantic fans lining up outside the suburban airfield to welcome the team home Sunday morning.

“It was incredible,” Mayor Zohran Mamdani said Sunday. “I mean, it’s hard to believe it was real, but it’s beautiful to wake up to know yes it was, and we’re the champions.”

In Astoria, firefighters blasted “New York, New York” from their rigs, while a massive crowd sang along to Alicia Keys “Empire State of Mind” en masse in Manhattan.

An MTA bus driver was caught on viral video dancing in front of a mob of jubilant fans.

“Even the bus driver on duty decided to pull over & get JIGGY!” one X poster wrote. “New York Knicks have brought back the energy to this city. Hopefully he doesn’t lose his job.”

Now-collectible editions of The Post flew off the shelfs throughout the five boroughs and the ‘burbs.

“One person bought all!” a worker at a deli Dry Harbor Avenue in Queens said Sunday. “Everyone wanted to buy today. They went crazy.”

Knicks point guard Jalen Brunson earned Finals MVP honors, but the series had plenty of heroes — including forward OG Anunoby, whose miraculous tip-in in Game 4 at MSG clinched that game and erased what was earlier a commanding 29-point Spurs lead.

Thursday’s parade guarantees that the party ain’t ending anytime soon.

“It will be a tremendous turnout,” said a retired NYPD supervisor who worked the mind-blowing New York Rangers and Yankees parades after they won national titles in the 1990s.

The parade will kick off at Battery Park at 10 a.m. and proceed north on Broadway — aka the Canyon of Heroes — and wind up at City Hall for a celebration hosted by the mayor.

“I think I’ll take the day off to go,” lifelong Knicks fan Andy Yu said of the upcoming parade. “I’ll just scream my lungs out during the parade when the bus [of players] goes past and seeing the trophy in person. It will be pretty special.”

Queens resident Victor Abreau said he’ll also play hooky.

“I’m calling out from work,” he said. “We are going to the parade, and we’re going to enjoy watching our city finally be part of the world championship. New York is finally back on top.”

City and police officials have not released estimates on how many fans they expect to show up, but past parades have erupted into citywide celebrations, including more than 4.5 million for the 1991 welcome celebration for returning Gulf War troops.

Other Big Apple parades — including for the Apollo 11 astronauts in 1969, astronaut John Glenn in 1962, Gen. Douglas MacArthur after his dismissal by Harry Truman in 1951 and Charles Lindbergh in 1927 after his famed flight — drew as many as 4 million spectators.

Additional reporting by Larry Celona, Joe Marino and Carl Campanile