Butler had 28 points, seven rebounds and six assists while Caleb Martin added 26 points and 10 rebounds to spark Miami, which will visit Denver on Thursday to begin the best-of-seven championship final.

Miami recovered from a gut-punch of a game-six defeat, where they fell on a last-second tip-in, to win the Eastern Conference final 4-3, silencing a loud Boston crowd.

Taking full advantage of an injury to Boston star Jayson Tatum in the opening seconds and a cold-shooting Celtics start, the Heat avoided becoming the first team in 151 attempts to lose a playoff series after leading 3-0.

"We stayed together as a group," Butler said. "We talked about going to get a tough one on the road and we did just that.

"But we're not satisfied. We're happy. We're ecstatic. But we've got one more to get."

Miami coach Erik Spoelstra said he never doubted his resilient squad could win game seven.

"Sometimes you have to suffer for the things you really want," he said. "This group has shown fortitude when there are inevitable let-downs and failures, but had that perseverance to pick yourself up, that collective spirit to keep on forging ahead."

The Heat, seeking a fourth NBA title and first since 2013, last reached the NBA Finals in 2020, losing to the Los Angeles Lakers.

The Nuggets, into the NBA Finals for the first time, swept the Lakers in the Western Conference final.

It was a determined effort by a Miami squad that lost to Boston in seven games in last year's East finals. Miami also lacked any momentum after squandering their 3-0 edge to set up a winner-takes-all road game.

"When the ship gets rocky, just stay together and keep believing in one another," said Miami's Bam Adebayo, who had 12 points and 10 rebounds.

Spoelstra said last year's loss had weighed on the team. "They made us get better. We thought about it all season long," he said.

Butler said his teammates enabled him to sink key shots and shut down Boston comeback bids.

"They give me so much confidence to hoop at a high level," he said. "They're the reason we're here. I know how good a team we are and we made it happen."

- 'A shell of myself' -

Tatum, who finished with 14 points on 5-of-13 shooting, turned his left ankle landing awkwardly after a baseline jumper in the opening seconds. He grimaced often and took only one shot in the first 17 minutes.

"It swelled up," Tatum said. "I was like a shell of myself. It was tough to move. It was frustrating especially that it should happen on the first play."

Miami stretched the lead as high as 17 points in the second quarter but Boston pulled within 59-51 early in the third.

Caleb Martin sank a baseline jumper to put Miami ahead 76-66 entering the fourth. Martin sank a three-pointer to ignite a 7-0 Miami run to open the fourth quarter for an 83-66 edge.

"Not shooting the ball well had an effect on us," Tatum said. "And it kind of snowballed."

The Celtics went nearly four minutes without scoring and never again threatened, finishing a woeful 9-of-42 from three-point range.

"They gave it everything they had," Celtics coach Joe Mazzulla said. "That's the most important thing to take from this. We failed, but it's not because the guys didn't have a sense of togetherness and character."

Jaylen Brown led Boston with 19 points but had a career-high eight turnovers while Derrick White added 18 points.

"We failed. I failed," Brown said. "We let the whole city down."

An 18-6 Heat run to close the first quarter gave Miami a 22-15 lead with the Celtics matching their season low for first-quarter points.

Boston went 0-for-10 from three-point range in the first quarter, missing the first 12 from beyond the arc overall, and made only 6-of-23 from the floor in the opening period.