BOSTON -- As Jayson Tatum connected on another 3-pointer midway through the third quarter Sunday -- en route to outscoring the Philadelphia 76ers in the period by himself -- he turned to a raucous Boston crowd and let out a cathartic yell.

"This is my s---," he said.

Tatum scored 51 points, the most in a Game 7 in NBA history, to lead the Celtics to a 112-88 victory to advance to the Eastern Conference finals. Tatum broke the record set two weeks ago by Stephen Curry, who scored 50 points in Game 7 of the Golden State Warriors' first-round series against the Sacramento Kings.

Tatum went 17-of-28 from the field and added 13 rebounds and five assists, becoming the fifth player in NBA history with at least 50-10-5 in a playoff game.

"It's a movie," Celtics guard Marcus Smart said. "It's a big movie. Being able to just sit back, eat your popcorn and watch."

After struggling through one of the worst shooting nights of his career in Game 6, Tatum responded with one of the best performances in franchise history. He scored or assisted on 62 points in Game 7, outshining the Sixers' star duo of Joel Embiid (15 points) and James Harden (nine points), who combined to score or assist for 44 points.

Tatum scored all 51 points in the half court, according to ESPN tracking data, against five different defenders, including 17 points against Embiid, the 2023 NBA MVP. Tatum finished fourth in the voting for the award this season, a career-best finish, but by the end of the game the sold-out crowd at TD Garden serenaded him with chants of "MVP."

Before the game, Tatum called Sunday a chance for the Celtics to redeem themselves after getting routed in their last game in Boston, drawing boos from the home crowd. Tatum had a dreadful start to Game 6, shooting 1-for-13 through the first three quarters before getting hot late.

"I was really excited just for the moment, to be able to come out and play today," Tatum said after Sunday's game. "It definitely was on my mind that I had played as bad as it could get for 42, 43 minutes. We have a saying, 'It's only up from here.'"

It was clear he was ready to respond from the beginning of Game 7. Tatum scored 25 points in the first half after scoring 18 points in the first half of Games 4, 5 and 6 combined.

"Going into Game 6 -- it sounds crazy, I was too locked in," Tatum said. "I was too tight. I was too in my own head thinking about what I need to do. How many points I need to score. It's a big moment.

"And today I was more myself. Pregame, I was relaxed, laughing, joking. That's when I play my best, when I'm having fun. I just tried not to think about the pressure, what everybody is going to say. Just focus on the game and having fun."

Still, the Sixers led after the first quarter and trailed 55-52 at halftime, staying in the game despite both of their stars struggling. Then Boston raced past Philadelphia in the third quarter, outscoring the Sixers 33-10 to break the game open. Tatum scored 17 points in the third quarter alone, nearly doubling the Sixers' total and pushing the game out of reach.

When asked if he'd seen a performance like Tatum's before in the playoffs, Sixers coach Doc Rivers said only one came to mind.

"I've seen one. And it was in this building, unfortunately," Rivers said. "And it was LeBron [James]. That's the only time I've seen a performance like that live and I'm glad that I haven't seen many. ... [Tatum was] unbelievable."

The Celtics advanced to the conference finals for the second consecutive season and the fifth time in the past seven seasons.

"A team that we're extremely familiar with," Tatum said about the matchup with Miami. "A very well-coached team, they compete with the best of them, play hard. They defend, they make plays and they figure out a way to win games. It's going to be fun; it's going to be highly competitive and I'm looking forward to it."

The Celtics rallied from down 3-2 in the series with two consecutive victories to close it out. It mirrored the situation the Celtics faced in last year's Eastern Conference semifinals, when Boston came back from down 3-2 vs. Milwaukee to advance to the conference finals.

The Celtics have now won seven series when trailing 3-2, the most by any team in NBA history, according to research by ESPN's Stats & Information.

"You always come into a series with the expectation of how it's supposed to go, and it's just not how the playoffs are," Celtics first-year coach Joe Mazzulla said. "We just handled the ebbs and flows of a series. Never got too emotionally high, too emotionally low. We had rough patches, but we were able to keep our emotional togetherness intact, which I think is important in the playoffs."

After losing in the NBA Finals last season, the Celtics have been relying on their experiences from that playoff run to carry them forward this season. The slogan "unfinished business" has been their rallying cry throughout the year, and it was displayed prominently on the video board prior to Game 7.

With the other top seeds in the conference eliminated, the Celtics opened as -500 favorites to beat the Heat (+380) at Caesars Sportsbook. And as the final seconds of the fourth quarter ticked off the clock, Boston fans had already turned their attention to the next task at hand, chanting, "Beat the Heat."

"We really locked in and stayed together," Celtics center Al Horford said. "[The Sixers are] a really good team. That could have easily been a conference final or if they were on the other side, it could've been a Finals match. They're that good of a team. And you've got to give them credit. They're a good team. One team had to win, and we were just able to get it done."