A key component from the Mets’ rotation last season is headed west to uncharted territory.

Luis Severino reached agreement Thursday with the A’s on a three-year contract worth $67 million, industry sources confirmed, as the organization prepares to begin play in Sacramento, Calif., for at least a three-season hitch before settling in Las Vegas.

Severino’s deal includes an opt-out after the second season. The guaranteed payout is the largest in A’s franchise history.

Severino, 30, declined a qualifying offer from the Mets worth $21.05 million, meaning the team will receive draft pick compensation for his departure. The compensatory pick will be after the fourth round.

A workhorse in the Mets’ rotation last season, Severino pitched to a 3.91 ERA over 182 innings in 31 starts.

The right-hander arrived on a one-year deal worth $13 million as he looked to resurrect a career that had been plagued by injuries with the Yankees.

The veteran pitcher was part of the fabric of a Mets team that rallied over the final four months of the season for a National League wild-card berth before advancing to the NLCS, which the Dodgers won in six games.

Severino was often in the middle of team celebrations, holding up the “OMG” letters that became a Mets trademark following Jose Iglesias’ arrival and the infielder’s release of a song by the same name.

Severino also endeared himself to Mets fans by revealing before the Subway Series in July that he was part of a text chain with his former Bronx teammates and responded to their taunts by saying the Yankees only have “two good hitters” — a reference to Aaron Judge and Juan Soto.

“Thank you new York @mets fans for all the support all year long,” Severino posted on X. “Thank you mets staff and [front] office for everything. I forever be grateful for an incredible season.”

Severino, Sean Manaea and Jose Quintana all hit free agency after the season to leave holes in the Mets’ rotation.

The Mets last week signed Frankie Montas to a two-year contract worth $34 million with an opt-out after next season to help fill one rotation void.

The Post’s Jon Heyman reported the A’s offered a “big” contract to the lefty Manaea (who started his major league career with the organization) before reaching agreement with Severino.

The Mets still have multiple rotation spots to fill.

As it stands, Kodai Senga and David Peterson are locked into next season’s rotation, along with Montas. Other possibilities include Tylor Megill, Jose Butto, Paul Blackburn and prospects Brandon Sproat, Nolan McLean and Blade Tidwell.

But president of baseball operations David Stearns likely will look toward a free-agent market with plenty of possibilities.

Corbin Burnes and Max Fried are among the high-end options available, but Stearns could take a similar course as last offseason and look for lower-risk deals.

Clay Holmes, who has spent most of his career as a reliever, is drawing interest as a starter, and the Mets are among the interested teams, according to sources.

Mike Soroka, who bounced between the bullpen and rotation last season for the White Sox and looks to rebuild his value, is another possibility for the Mets.

The Mets also could trade for an established starter, using the organization’s positional prospects as chips. It’s a group that includes Brett Baty, Luisangel Acuña, Ronny Mauricio and Jett Williams, among others.