Diego Nicolás Cristin (born 5 April 1981) is a former professional tennis player from Argentina.

A right-handed player, Cristin comes from the Núñez neighbourhood of Buenos Aires.

[1] In 2003 he had the distinction of being the first player to beat future US Open winner Juan Martín del Potro in a professional match, which he did at a local satellite tournament.

[2] He was unable to break into the ATP Tour, featuring only as high as Challenger level.

As a doubles player he made the world's top 200 and won a Challenger tournament in Santiago in 2009, partnering Eduardo Schwank.