Efraín Nieves (born November 15, 1989) is a Puerto Rican professional baseball pitcher who is a free agent.

After playing rookie ball in 2007 and 2008, Nieves was promoted to the Single-A Wisconsin Timber Rattlers for the 2009 season.

[3] On December 6, 2012, Nieves was selected by the Toronto Blue Jays in the minor league phase of the Rule 5 Draft.

In his first Frontier League start on May 20, 2015, Nieves pitched six innings of one hit, no runs ball with five strikeouts.

[7] On June 22, 2017, Nieves signed with the Somerset Patriots of the Atlantic League of Professional Baseball.