EAST RUTHERFORD, N.J. — Believe it, Seattle — after 38 years, the Seahawks are finally Super Bowl champions.

In fact, by the time it ended, the only thing unbelievable about this one was how easy it was, as the Seahawks cruised to a 43-8 win over the Denver Broncos to take Super Bowl XLVIII in front of 82,529 at MetLife Stadium on Sunday night.

A young and brash Seattle defense made Peyton Manning and Denver’s record-setting offense merely look old and slow, dominating the action from the start and forcing two first-half turnovers as the Seahawks jumped out to a 22-0 halftime lead, the third-largest in Super Bowl history.

Percy Harvin then ended any thoughts of a Denver comeback as quickly as possible, returning the opening kickoff of the second half 87 yards for a touchdown to give Seattle, which entered the game as 2.5-point underdogs in most sports books, a 29-0 lead.

Harvin’s touchdown, as did a safety on the first play of the game, came 12 seconds into the half — a symmetry that Seattle’s fans, the self-named 12’s, surely found fitting on a day when everything went the Seahawks’ way.

The Super Bowl title is the first championship for a Seattle team in one of the four major professional sports leagues since the now-departed Sonics captured the NBA title in 1979.

And it came in the Seahawks’ second Super Bowl appearance, Seattle having lost to Pittsburgh 21-10 in Detroit following the 2005 season.

The game turned Seattle’s way from the start, as a mis-timed snap on Denver’s first offensive play led to a Seahawks safety, credited to Cliff Avril, just 12 seconds into the game — the fastest score in Super Bowl history.

Seattle turned the ensuing possession into a field goal, and then after forcing a three-and-out, drove for another field goal.

Then came a pair of back-breakers forced by the Seattle defense.

Late in the first quarter, Manning threw a wobbly pass over the middle under heavy pressure into the hands of Seattle safety Kam Chancellor.

That led to a 1-yard-touchdown run by Marshawn Lynch that put Seattle ahead 15-0 with exactly 12 minutes remaining in the second quarter.

At that point in the game, Seattle had a 165-11 edge in yards and 9-0 in first downs.

Denver finally got a couple first downs on its initial drive of the second quarter.

But on a third-and-13 from the 35, Manning was hit by Avril as he threw with the ball falling into the hands of linebacker Malcolm Smith, who had an easy path to a 69-yard touchdown that made it 22-0 with 3:21 left in the first half, and had the non-Seahawk fans in the crowd beginning to look to the Bruno Mars halftime show to make it interesting again.

Then came Harvin’s return, sparking a second half that increasingly had the feel of a Seahawks home game as orange-clad Denver fans began to leave in droves.

Seattle scored again with 2:38 to play in the third quarter when Russell Wilson — on this day, a quiet star — to make it 36-0.

Denver averted the embarrassment of potentially suffering the first shutout in Super Bowl history when Demaryius Thomas scored on a 14-yard pass on the final play of the third quarter.

But it was a momentary intrusion into Seattle’s fun. Wilson threw a 10-yard pass to Baldwin early in the fourth quarter to make it 43-8 as the party on the Seahawks sideline kicked into high gear in what might be the greatest moment in the history of Seattle sports.

The Seahawks had been as far as a conference title game just twice since entering the NFL in 1976 before this season, a year that began with high expectations after a young team began to find itself late in the 2012 season to advance to the Divisional round.

Seahawks players, in fact, began talking Super Bowl the minute they lost in Atlanta a year ago, and Seattle was a popular pick among pre-season prognosticators.

Still, some wondered how a team that ended the season as the seventh-youngest in the NFL would handle the hype.

Turns out, they did it “very well,” the joking response coach Pete Carroll often gives to questions about how he thinks his team will handle something.

The win also gave Carroll a slice of coaching history as he became just the third coach to win both a college national title and a Super Bowl — the others being Jimmy Johnson (Miami, Dallas Cowboys) and Barry Switzter (Oklahoma, Dallas Cowboys).

The Seahawks turned to Carroll after the 2009 season, Seattle having won just a combined nine games in the previous two years, and surprisingly firing coach Jim Mora after just one season.

Carroll, who had twice been fired by NFL teams (Jets, Patriots) before rehabbing his career at USC, was anxious to show he could succeed at the highest level of the game.

He, too, set a high bar when the season began, saying the team expected it could get to, and win, the Super Bowl.

And if there was a time that seemed an unbelievable thought, it doesn’t anymore.