BOSTON — It took 44 years, but the Philadelphia 76ers have finally beaten the Boston Celtics in a playoff series.

Behind arguably the best playoff performance of Joel Embiid’s career, the 76ers claimed a heart-stopping 109-100 victory in Game 7 of their Eastern Conference quarterfinal series. Philadelphia also became the 14th team in NBA history to come back from a 3-1 deficit to win a best-of-7 series.

“It feels good to win,” Embiid said. “Obviously, we got a bigger goal in mind. But finally beating these guys feels pretty good.”

Before Saturday’s win, the 76ers had gone an NBA-record 0-18 when trailing 3-1 in a series. Boston was 32-0 when holding a 3-1 series lead.

Philadelphia beat Boston in the playoffs for the first time since 1982, snapping a streak of six consecutive series losses — the last three of which included Embiid. The two teams have played each other in 23 series, more than any other matchup in NBA playoff history.

Behind Embiid’s 34 points, 12 rebounds and six assists and Tyrese Maxey’s 30 points, 11 rebounds and seven assists — making them the first teammates in NBA history to each have at least 30-10-5 in a Game 7 — the 76ers finally broke through against one of their oldest rivals.

“I just really wanted the ball,” Maxey said of his late-game heroics. “Early in the fourth, we went to Joel, and I just felt like it was time for me to step up and make a play.”

The 76ers advance to the Eastern Conference semifinals, where they will take on another longtime nemesis, the New York Knicks, who knocked Philadelphia out of its last trip to the playoffs two years ago. That series will begin Monday.

The Celtics were dealt a blow hours before tip-off Saturday, when they ruled out Jayson Tatum for Game 7 because of left knee stiffness.

“He just came in today with knee discomfort,” Celtics coach Joe Mazzulla said during his pregame media availability a few minutes after Tatum was officially ruled out. “And we decided, the medical staff and myself, that he would not play.”

Without Tatum, Mazzulla started Derrick White, Baylor Scheierman, Jaylen Brown, Ron Harper Jr. and Luka Garza, a lineup that had never played together before the biggest game of Boston’s season. That unit was outscored by seven points to open the game, and Boston was fighting uphill virtually the rest of the way. Mazzulla never went back to the lineup.

“Yeah, I mean, I thought there was a couple of things we saw tactically we wanted to test out, you know, obviously give the series a little bit of a different feel and take advantage of the roster that we’ve had and take advantage of the guys that can impact plays and whatnot,” Mazzulla said about his starting lineup after the game. “So, I thought it was great by the guys, and we came up short.”

Philadelphia jumped out to an early 15-point lead in the first quarter, but Boston erased that deficit in the second, taking its only lead of the game. The 76ers reasserted control late in the second quarter and throughout the third.

The 76ers went on a 14-3 run — much of that occurring with Embiid on the bench — late in the third quarter and pushed their lead to 84-66. But the Celtics stormed back, pulling to within one point on four different occasions in the fourth quarter.

Philadelphia’s offense bogged down for much of the quarter, and the Celtics, riding the energy provided by a raucous sellout crowd, appeared as though they might hand the 76ers another devastating loss.

After Brown’s bucket cut the 76ers’ lead to 97-96 with 5:02 remaining, Boston missed 10 consecutive shots. And though Philadelphia also missed a few shots during that stretch, Maxey made back-to-back layups that put the game out of reach.

“Yeah, it was great,” 76ers coach Nick Nurse said. “Obviously, they were very timely, and he hadn’t turned on the jets much all night … but then he made a couple, and they were huge.”

While Philadelphia enjoyed finally getting the best of Boston in the playoffs, the Celtics were trying to wrap their heads around how quickly their season had ended. Six days ago, the Celtics demolished the 76ers 128-96 at Philadelphia in Game 4 to spoil Embiid’s return.

At that point, hardly anyone expected the 76ers to battle back.

But they did, thanks in part to Tatum being unavailable in Game 7. Boston heads into the summer having failed to advance out of the first round for just the second time in the past decade. The Celtics hope that a full offseason for Tatum to recover from his righty Achilles tear, which occurred a year ago this week, and some offseason additions will have them contending for a championship again next year.

For their part, though, the Celtics were defiant about their season, and their approach.

“No feelings of regret whatsoever,” said Brown, who led Boston with 33 points, nine rebounds, four assists and three blocks. “Obviously, we would have liked to close it out … but Philadelphia is a good basketball team, and they’ve gotten better since the regular season.

“It’s the playoffs. We knew it was going to be a fight, and we didn’t expect nothing less. Nothing to hang our head over. Got no regrets.”