Roberto Gabriel Grau (18 March 1900 – 12 April 1944) was an Argentine chess master.

In 1921/22, he tied for 3rd–4th (ARG-ch 1 Mayor; Damian Reca won).

In 1938, he tied for 5-6th in Montevideo (Carrasco), an event won by Alekhine.

In 1939, he took 4th, behind Fenoglio, Guimard and Julio Bolbochán, in Rio de Janeiro.

In 1939, he took 7th in Buenos Aires (Miguel Najdorf and Paul Keres won).

He was one of the original signatories in the formation of FIDE at Paris 1924 (1st unofficial Chess Olympiad).