Red and white confetti was falling from the roof.

Booming chants of “Let’s go Johnnies” were echoing from one side of a sold-out Madison Square Garden to another.

Zuby Ejiofor, seventh-ranked St. John’s workhorse of a center, lifted the Big East regular-season trophy as high as he could as highlights of this magical season played on the scoreboard.

Forty years later, St. John’s was on top of its conference by itself, and everyone was soaking it in after this clinching, rock fight of a 71-61 victory over Seton Hall on Saturday.

“We got to experience the energy in the arena and it’s a surreal feeling,” Ejiofor said after the Red Storm completed their first perfect season at home (18-0) since 1931-32. “I haven’t really had the pleasure of being an impact player and winning championships. So to be able to do that in such a prestigious program and to see the history behind it as well, it means a lot. Not just to me and my teammates, but obviously to the whole community as well.”

St. John’s (26-4, 17-2) made its fans wait four decades for another outright Big East regular-season title, and it made them sweat for the clincher.

What, you thought it was going to be easy?

It certainly wasn’t, even against seven-win Seton Hall. Very little has come easy for this team, but as has been the case throughout this magical season, the Johnnies found a way to prevail.

They overcame off shooting nights from star guards Kadary Richmond and Deivon Smith and the absence of starting forward Aaron Scott (hamstring) by owning crunch time yet again.

Ejiofor and RJ Luis, the two key returnees from coach Rick Pitino’s first season, led the way in combining for 38 points and 16 rebounds.

Sadiku Ibine Ayo added eight points and five rebounds off the bench in place of Scott.

St. John’s dominated the final 10:01, outscoring Seton Hall, 22-12, from that point on.

The Pirates (7-22, 2-16) managed just five points over the last 5:22.

“It’s a really proud moment,” Ejiofor said. “It’s a testament of the work that we put in the whole season, from the preseason until now. We all believe that we could get to this moment. Coach Pitino talks a lot about getting on Broadway, and seeing what you can do when you get to that point.”

It was a second straight sluggish performance, following Wednesday’s narrow win at Butler.

St. John’s committed 16 turnovers, five over its season average, and missed 12 free throws. Richmond and Smith were a combined 6 of 21 from the field.

“The pressure was on our guys the last two games — big time,” Pitino said. “I could see it. … For them, because they’ve never been in these situations before, you need it so they can learn it.”

It was even at 49 after an Isaiah Coleman jumper with 10:01 left. The Garden was comatose. A few possessions later, Ruben Prey’s 3-pointer woke up the large crowd.

Then, Smith scored inside to push the lead to five and force a Seton Hall timeout.

It was finally getting loud, and would get even louder.

Luis turned a steal into an explosive transition dunk and Richmond and Ejiofor added baskets inside. The lead was seven.

“We are New York strong,” Pitino said. “We don’t win the prettiest way, but we’re New York tough. And we’re very proud of that.”

Soon, confetti was falling. St. John’s was posing for photos with the trophy and the Johnnies’ fans were celebrating a title decades in the making.

The team didn’t cut down the nets, partly because the regular season isn’t over.

Next up is a trip to No. 21 Marquette next Saturday. Then comes the Big East Tournament and the NCAA Tournament.

There are bigger games ahead.

“Get ready — everybody get ready,” Pitino told the euphoric St. John’s fans during the celebration. “We’re just getting started.”