MIAMI >> LeBron James finally got a Game 7 victory, on his third try.

Next up, the NBA finals — and his third try at that elusive first championship. A year after watching someone else celebrate on their home floor, the Miami Heat were the ones dancing at midcourt.

James had 31 points and 12 rebounds, Chris Bosh hit a career-best three 3-pointers — the last sparking the run that put it away — and the Heat won their second straight Eastern Conference title by beating the Boston Celtics 101-88 in Game 7 on Saturday night.

Miami opens the title series in Oklahoma City on Tuesday night. The Heat got there by outscoring Boston 28-15 in the fourth quarter, with the "Big Three" of Dwyane Wade, Bosh and James scoring every Miami point.

"We decided to come together and play together for a reason," Wade said.

Wade scored 23 points, Bosh finished with 19 and Shane Battier added 12 for the Heat, who won a Game 7 for the first time since 2004 — Wade’s rookie season. Now it’s back to the finals, where Miami fell in six games to Dallas a year ago.

Rajon Rondo finished with 22 points, 14 assists and 10 rebounds for Boston, which got 19 points from Paul Pierce in what might be the last game of the "Big Four" era for the Celtics.

Boston took out its starters with 28.3 seconds left. By then, workers already had a rope around the perimeter of the court, preparing for the East trophy presentation.

"Give them credit," Rondo said. "They spread the points out as a team tonight. Give them credit. They played great tonight as a team and we just came up short."

When Heat President Pat Riley was shown on the giant overhead video screen in the moments just after the final buzzer, the crowd screamed. Riley finally acknowledged them with some claps, before the 2012 Eastern Conference champions logo was shown as players below the scoreboard high-fived and hugged, all wearing the new T-shirts and caps that marked the accomplishment.

The screams kept coming, first when Alonzo Mourning took the microphone — "We still got a lot of work to do," Mourning said — and then again when he handed the trophy to Heat owner Micky Arison.

"A roller-coaster ride," Arison said.

A roller-coaster game, too. In a roller-coaster season.

All worth it — for now, anyway. The next step awaits, another shot at the finals. In a championship-or-bust season, the Heat board a plane for Oklahoma City on Sunday.

"We have been through a lot," Heat coach Erik Spoelstra said.

James and Celtics coach Doc Rivers — who teared up often postgame — shared a long embrace when it was all over. Before coming to Miami for Game 7, Rivers had packed for Oklahoma City, a trip he won’t make, set to now spend his time seeing if James can win that first title.

"I told him to go do it," Rivers said.

Down by seven at the half and eight early in the third quarter, Miami started clawing back. An 8-0 run tied it at 59-all, capped by Wade hitting a jumper, and then the fun really started.

There were six lead changes and five more ties in the final 7 minutes of the third. Bosh scored with 29 seconds left for the last of those ties, and it was 73-all going into the fourth.

Six games decided nothing, and nothing was decided in Game 7 until the very last moments, neither team yielding much of anything. Battier’s 3-pointer with 8:06 left in the third cut Boston’s lead at the time to 59-57.

And back and forth they went.

For the next 13 minutes, a span of 46 dizzying, unbelievable possessions, neither team led by more than two points.

That finally changed when Bosh his third 3-pointer with 7:17 left. James made a runner on the next Miami trip, and suddenly the Heat had their biggest lead of the night to that point, 88-82 with 6:54 remaining.

They were on their way.

"He was big time — every shot, every defensive play, every rebound — we missed him," James said of Bosh. "We’re just happy to have him back at the right time. If it wasn’t for him and the rest of the guys that stepped up, we don’t win this game."

Said Spoelstra: "Our most important player."

James made a 3-pointer — it went into the books as a 30-footer, as he leaped from atop one of the Eastern Conference finals stickers on the floor — as the shot clock was expiring with just under 6 minutes left, making it 91-84.

"Backbreaker," Rivers said.

Even mistakes were going Miami’s way, as James lost a behind-the-back dribble, only to have the ball skip right into Battier’s hands.

Bosh scored from inside the lane to end that possession. Wade scored on the next one, the lead was 95-86 with 3:23 left, Boston called time and the building was simply rocking. James did plenty of talking on the Heat bench in that stoppage, clearly saying the word "Finish" at one point.

They listened. A three-point play by Wade with 2:53 left all but sealed it, the Heat were up 12, and Oklahoma City beckoned.

"We had nothing left," Rivers said. "That’s how it felt, as a coach. … But overall, I don’t know if I’ve ever had a group like this."

Brandon Bass scored 16, Ray Allen finished with 15 and Kevin Garnett scored 14 for the Celtics, who know next season could bring big changes.

A team that was under .500 at the All-Star break almost made the NBA finals.

Almost.

"One game away on the road, banged up. … I don’t know if we could have gotten any more from the group," Rivers said.

Boston’s first score came when the Celtics were inbounding from under their own basket with 1.2 seconds left on the shot clock. Rondo surveyed the defense, then decided to simply toss the ball off Wade’s back, catch it and score himself.

It was an omen — the Celtics got plenty of easy scores early.

Boston ran out to a 23-14 lead, before the Heat settled down and tied it twice in the second quarter, the last of those at 35-all with 6:50 left. It was then that Garnett left with his third foul. Heat on a run, Garnett going to the bench, so momentum Miami, right?

Not quite.

Bass scored 10 points in a stretch of just over 3 minutes to spark a 14-3 run, with the Celtics scoring three times off turnovers in that stretch. Allen waltzed in unbothered for a layup with 22 seconds left in the half, and Boston took a 53-46 lead into the break. And the least surprised person in the arena was Rivers, who sensed at the morning shootaround that his team would be sharp for Game 7.

They were.

Just in the end, Miami was sharper.

"That’s what we talk about," said James, who lost Game 7 appearances with Cleveland in 2006 and 2008. "It has to be a collective group to win the championship. Everybody was in tune today. We wanted to give our fans a big win. We look forward to the next challenge."

NOTES: Strange but true: Celtics fans in leprechaun outfits — green glittery vests, bow ties and hats — posed for photos with fans during the game. They were seated directly behind Arison. … Also strange but true: Manny Pacquiao — from the Philippines, the country where Spoelstra’s mother hails from — planned to delay the start of his fight Saturday night so he could see Game 7. Pacquiao is a Celtics fan. … It was Heat F Udonis Haslem’s 32nd birthday. … Former Heat forward Jamal Mashburn and former Red Sox slugger Mo Vaughn chatted near the Boston bench before the game.