Thomas Mark Wilhelmsen (born December 16, 1983) is an American former professional baseball relief pitcher.

He played in Major League Baseball (MLB) for the Seattle Mariners, Texas Rangers, and Arizona Diamondbacks.

Wilhelmsen graduated from Tucson High School,[1] whence he was selected by the Milwaukee Brewers in the seventh round (199th overall) of the 2002 MLB Draft.

[3] He played for the AZL Mariners, Everett AquaSox and Clinton LumberKings that season, going a combined 7–1 with a 2.19 ERA in 15 games (12 starts).

On May 17, 2011, after being signed by the Mariners he was optioned to Class AA in order to clear room for Franklin Gutierrez to be activated.

After a series of trades created an opening on the Mariners' 25-man roster, Wilhelmsen was recalled from the minor leagues on August 2, 2011.

[6] He won his first major league game on August 15, pitching a perfect 8th inning against the Toronto Blue Jays.

On June 8, 2012, Wilhelmsen recorded the save in a six-pitcher combined no-hitter which was started by Kevin Millwood who left the game after the 6th inning due to a groin injury.

[10] On November 16, 2015, the Mariners traded Wilhelmsen, James Jones, and a player to be named later (Patrick Kivlehan) to the Texas Rangers for Leonys Martín and Anthony Bass.