Casey Michael Fien (/fiːn/ feen;[1] born October 21, 1983), is an American former professional baseball pitcher.

He played in Major League Baseball (MLB) for the Detroit Tigers, Minnesota Twins, Los Angeles Dodgers, Seattle Mariners, and Philadelphia Phillies.

[4] On February 23, 2010, Fien was designated for assignment to make roster room for the newly acquired Johnny Damon.

On July 4, 2012, Fien was called up to the majors from the Triple A Rochester Red Wings, after the Twins optioned Nick Blackburn.

[12] On July 8, 2012, Fien made his debut with the Twins, pitching a scoreless 8th inning against the Texas Rangers.

He was designated for assignment on May 2, he cleared waivers and was sent outright to Triple-A Tacoma Rainiers the next day.

On May 9, 2017, the Philadelphia Phillies acquired Fien via trade from the Seattle Mariners for cash consideration and assigned him to the AAA Lehigh Valley IronPigs.