Jayson Tatum says the Boston Celtics' 18th NBA title is a "night I will remember for the rest of my life".

The Celtics capped a dominant season by cruising to a 106-88 victory over the Mavericks in Game 5 of the NBA finals on Monday, capturing their first league championship since 2008.

After recording the league's best regular-season record at 64-18, Boston continued that fine form in the post-season, going 16-3 to earn their record-breaking 18th title, moving them above the Los Angeles Lakers.

After losing Game 4 on the road, the Celtics responded in style, with Tatum the standout performer, getting 31 points, eight rebounds and 11 assists.

"I mean, this is going to be a night that I will remember for the rest of my life, from the game, the celebration, these moments," Tatum said.

"Over the last couple years, we had some tough losses at home in the playoffs. We've lost the NBA championship at home in front of our fans. We had a chance to beat Miami in Game 6 a few years ago and lost that one.

"So, to have a big win - the biggest win that you could have in front of your home crowd - I felt like that was really important to go out there and do everything in my power to make sure we won this game tonight."

"It means the world," Tatum said on stage. "It's been a long time. And I'm grateful."

Kristaps Porzingis missed Games 3 and 4 with a leg injury but managed 16 minutes off the bench to help his team to victory in the decider.

He confirmed after the game that he would need surgery on the injury but did not want to miss out on the occasion.

"I think something could have happened, for sure, especially compensating now on the other leg now, which I just came back from," Porzingis told ESPN.

"There was definitely some added risk, but I didn't care. I was like, 'I want to give everything I can and then fix it after if I need to.'"

"Since last game, I've been thinking ... 'How can I get my body ready for next game?'. Like, no matter how it is. And today I was like, 'I'm going to try everything possible to get out there.'

"And, man, it feels great to be a champion."