Ramón A. Nivar Martínez (born February 22, 1980) is a former Major League Baseball utility player who played for the Texas Rangers and Baltimore Orioles from 2003 to 2005.

Nivar made his Major League debut on July 30, 2003, for the Rangers against the Boston Red Sox as a ninth inning defensive replacement.

Before 2006 Nivar signed a minor league contract with the St. Louis Cardinals but did not make the roster.

He played some games for the independent York Revolution in 2007 and then signed a minor league contract with the San Diego Padres at the end of the season.

In 2009, Los Angeles Dodgers signed Nivar to a minor league contract and assigned him to Double-A Chattanooga Lookouts.