ORLANDO, Fla. — The Orioles set out to acquire a major addition to their lineup and, on the final day of the winter meetings, they have done so.

Baltimore is signing first baseman Pete Alonso to a five-year, $155 million contract, a source confirmed. It marks the largest deal signed during president of baseball operations Mike Elias’ seven-year tenure, and it signals a major investment from the ownership group led by David Rubenstein.

It’s the second-largest contract in terms of overall value in Orioles history, following Chris Davis’ $161 million extension a decade ago.

Alonso’s deal, which was first reported by ESPN, includes a limited no-trade clause, the source said. It does not include any opt-outs or deferred money. The signing is pending a physical.

This is the largest deal ever for a first baseman in terms of average annual value, and it comes a day after Baltimore missed out on Kyle Schwarber, who re-signed with the Philadelphia Phillies.

Alonso hit 38 homers with a .272 average last season for the New York Mets and has a career .516 slugging percentage.

His addition to the lineup could have a positive ripple effect on multiple hitters. It takes pressure off Gunnar Henderson to be the main offensive threat and injects power into a lineup that struggled to produce runs. Baltimore managed the 24th-most runs in baseball last season.

From July onward, the Orioles were less of a power threat, too, but that had much to do with injuries and the departures of hitters at the trade deadline.

Alonso’s bat speed is a promising sign. His average speed of 75.3 mph ranked in the 91st percentile, which helped translate to his average exit velocity of 93.5 mph (97th percentile, according to Statcast).

“Our lineup underperformed their talent level last year, so just kind of injecting more hitting talent into the batting lineup is kind of item No. 1, and the positional aspect is something that we can adjust to after IDing the hitter we want to bring in,” Elias said Monday.

The 31-year-old Alonso is a below-average defensive first baseman, so he may see ample time at designated hitter. But the signing creates a logjam at first base with Coby Mayo, Ryan Mountcastle and Samuel Basallo. This could lead to a trade involving one of the right-handed hitters in that group (Mayo or Mountcastle) to add pitching.

The Orioles backed up their desire to add a major bat by offering five years and $150 million to Schwarber — the same contract offered by the Phillies.

“We’re talking to a whole bunch of hitters, and we just view it as, ‘Do they improve the team? Do they improve the roster? Do they raise the ceiling of the team, and do they have an impact?’” Elias said Monday. “And, if the player is good enough, we can figure out ways to accommodate them, so we have a lot of conversations going on, mostly in free agency, but also some in trades, on guys we view as impact bats.”

Elias also said he thinks Baltimore has the payroll flexibility to add a major rotation piece.

The Orioles are still aggressive in the pitching market. Their offseason is not done.

This has been a busy offseason for Baltimore, which has signed or traded for five players. The Orioles have added right-handers Andrew Kittredge and Ryan Helsley and outfielders Taylor Ward and Leody Taveras in addition to Alonso.

This article has been updated.