It took all 82 games, and an answered prayer on Tuesday night, before the Islanders finished the job Wednesday.

It took three comeback victories over the Penguins and the first season sweep in franchise history against Pittsburgh.

It took three wins in the final four games of the season, two months of .680 hockey without star center Mathew Barzal and a run of sheer excellence from goaltender Ilya Sorokin.

And it took a white-knuckle third period against the Canadiens in the very last game of the regular season.

But the Islanders got it done, and that is all that matters.

For the fourth time in five seasons and the first time since they began playing at UBS Arena, the Islanders will be in the playoffs after Brock Nelson scored twice and they beat the Canadiens 4-2 on Wednesday night.

The Islanders will face either the Bruins or Hurricanes in the first round of the playoffs, depending on the outcomes of those team’s games Thursday.

Finishing the 2022-23 season with a 42-31-9 record, the Islanders did just enough to keep the Penguins out of the playoffs for the first time since 2006.

They also became the fifth of five New York City-area hockey and basketball teams to make the playoffs this season; the only other time that happened was 1994.

Going into the third period Wednesday night, the Islanders needed merely to hold onto a 3-2 lead.

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And, despite wave after wave of nervous energy rolling through the building, the Islanders played a structured and defensively impeccable 20 minutes, throwing themselves in front of shots and managing the puck without issue.

Sorokin, who has so often stood between the Islanders and disaster this season, needed to make just 16 saves for the win.

Anders Lee sealed it with a power-play goal — the Islanders’ first in 19 tries and nearly three weeks — tipping Sebastian Aho’s shot in at 16:01 of the third period.

That nervous energy quickly turned to a chant from the fans in the arena: “We want playoffs!”

And now, the fans have got playoffs.

After control of their own destiny slipped through their fingers with a disastrous 5-2 loss at Washington on Monday night, the Islanders could not and did not let a second chance slip through their fingers.

The Canadiens didn’t record a shot on net for more than eight minutes, with the Islanders skating at playoff intensity and UBS Arena as loud as it’s been in the building’s short history.

Nelson opened the scoring 10:26 into the first period, beating Sam Montembeault with a left-circle wrister off the rush.

Rem Pitlick tied the score just over seven minutes later, finishing a pass from Jake Evans after Noah Dobson’s defensive zone turnover, but almost immediately, the Islanders pulled back ahead.

Hudson Fasching cleaned up the garbage off Zach Parise’s rebound at 18:57 of the first to send the Islanders into the first intermission with a 2-1 lead.

Nelson added to that at 10:20 of the second, deflecting Dobson’s shot from the high slot for his 36th goal of the season.

Everyone in the vicinity gasped at 16:38 of the second, when Nick Suzuki boxed out the Islanders’ Samuel Bolduc and flipped the puck past Sorokin with one hand on his stick for a shorthanded goal to pull Montreal within 3-2.

But that did not knock the Islanders off course, and by the end of the game, even the power play had delivered.

Making the playoffs was a bare-minimum requirement for the Islanders, who finished the regular season with 93 points.

It is, however, a large monkey off the organization’s back following a disastrous 2021-22 campaign and a playoff race this season in which the Islanders looked out of it at various times, including after a 5-2 loss Monday to the Capitals.

Thanks to the Penguins’ own shambolic 5-2 loss to the Blackhawks on Tuesday, the Islanders regained control of their own destiny.

This time, what followed was nothing resembling a letup.