LOS ANGELES — In their comeback season, the Boston Celtics saved the biggest one of all for the NBA finals.

Boston rallied from a 24-point deficit and beat the Los Angeles Lakers 97-91 today to take a commanding 3-1 lead in this history-rich series and move within one victory of a 17th championship that seemed impossible a year ago.

A rivalry between the league's two most storied franchises — with some of the game's biggest names and biggest moments — now has its biggest rally.

No team had ever overcome more than a 15-point deficit in the first quarter, and although the league doesn't have a record for the largest rally in a finals game, the Celtics staged one that will forever be remembered in the annals of Celtics-Lakers lore.

When the final horn sounded, Paul Pierce, an L.A. kid playing in front of family and friends, doubled over in exhaustion and exuberance. The Celtics, the team he stuck with through 10 years, including a 24-win season in 2006-07, had done the impossible.

"We sucked it up," Pierce said. "We said we weren't going to back down.

"At the end of the third quarter I looked up at the scoreboard and told the fellas, 'We just have to go out there and compete and let the chips fall where they may."'

Pierce scored 20 points, Kevin Garnett had 16 points and 11 rebounds and Ray Allen had 19 points as Boston's Big Three, thrown together last summer by general manager Danny Ainge to revive a franchise accustomed to hanging banners from the rafters, put the Lakers on the brink of a summer vacation.

It took an epic comeback to do it, and now the Celtics can reclaim their place atop pro basketball with a win in Game 5 on Sunday night in Los Angeles.

No team has ever recovered from a 3-1 deficit in the finals.

"It can always happen. We aren't counting on that statistic," Pierce said. "We want to take care of this on Father's Day."

Kobe Bryant scored 19 points on 6-of-19 shooting but the league's MVP couldn't rescue the Lakers when they needed him most. Lamar Odom had 19 points — 15 in the first half — and Pau Gasol, whose addition in a midseason trade was supposed to give the Lakers their final piece to complement Bryant, had 17 points and 10 rebounds.

Trailing by 18 points at halftime and seemingly done when they fell behind by 20 with 6:04 left in the third quarter, the Celtics outscored the Lakers 31-15 in the third quarter to pull within 73-71 going into the fourth.

The remarkable rally was reminiscent of what Los Angeles did in Game 2, when the Lakers trimmed a 24-point deficit to two in the fourth quarter before the Celtics regrouped to open a 2-0 lead. But Boston had another 12 minutes to finish off theirs, and the green-and-white did.

Boston's comeback included a 21-3 run over the final five minutes, fueled by two 3-pointers from Eddie House, who was getting more playing time because of Rajon Rondo's tender left ankle. The Celtics were still down by double digits with 2 minutes left in the third but closed the quarter with a 10-1 run, capped by P.J. Brown's dunk — a slam that could be felt all the way back to Boston's North End.

The Celtics finally caught the Lakers at 73-all on Leon Powe's jumper in the lane with 9:05 remaining, tying the score for the first time since it was 2-2 in the first minute.