Oswaldo Antonio Mairena (born July 30, 1975) is a former Major League Baseball relief pitcher for the Chicago Cubs and Florida Marlins.

[2] He spent the first half of 2000 with Norwich until July 21, when he was traded with Ben Ford to the Chicago Cubs for Glenallen Hill.

[3] In 2001, Mairena was traded during spring training to the Florida Marlins for Manny Aybar, and split the season between the Calgary Cannons and Portland Sea Dogs.

Mairena was released from the team after 2003, and spent 2004 with the Uni-President Lions of the Chinese Professional Baseball League.

[2] He spent 2005 in the Mexican League, splitting the season between the Guerreros de Oaxaca and Vaqueros Laguna, and ended his professional career representing Nicaragua at the 2005 Baseball World Cup and the 2007 Pan American Games.