Zachary Martin Rosscup (born June 9, 1988) is an American professional baseball pitcher who is a free agent.

He has previously played in Major League Baseball (MLB) for the Chicago Cubs, Colorado Rockies, Los Angeles Dodgers, Seattle Mariners, and Toronto Blue Jays.

Rosscup made his professional debut with the rookie-level Princeton Rays, posting a 3-4 record and 2.68 ERA in 10 games.

In 2010, Rosscup split the season between the GCL Rays and the Low-A Hudson Valley Renegades, accumulating a 3-1 record and 2.64 ERA in 12 appearances, 8 of them starts.

[2] On January 8, 2011, the Rays traded Rosscup alongside Matt Garza and Fernando Perez to the Chicago Cubs in exchange for Sam Fuld, Chris Archer, Hak-Ju Lee, Brandon Guyer, and Robinson Chirinos.

Rosscup split the 2012 season between the AZL Cubs, Single-A Peoria Chiefs, and Double-A Tennessee Smokies, pitching to a 2-1 record and 3.45 ERA with 45 strikeouts in 31.1 innings of work between the three teams.

He made his MLB debut the same day, pitching two-thirds of an inning and allowing no runs against the Miami Marlins.

[9] Rosscup made his Rockies debut against the New York Mets at Citi Field on July 14 to pitch in relief for Jon Gray, who left the game in the third inning.

Rosscup split the remainder of the year between Colorado and the Triple-A Albuquerque Isotopes, posting a 5.14 ERA in 9 games with the Rockies.

[17] On June 2, Rosscup was assigned outright to the Triple-A Buffalo Bisons, but elected free agency rather than report.

[28] On August 25, 2020, Rosscup signed another minor league contract with the Colorado Rockies organization,[29] who added him to their 60-man player pool.

[35] On June 17, 2023, Rosscup signed with the Spire City Ghost Hounds of the Atlantic League of Professional Baseball.

[36] In 22 games (10 starts) for the Ghost Hounds, he registered a 4–4 record and 3.31 ERA with 84 strikeouts and 7 saves in 70+2⁄3 innings pitched.

[37] On October 23, 2023, Rosscup was selected in the seventh round by the Mumbai Cobras, with the 51st overall pick, of the 2023 Baseball United inaugural draft.