Isaías "Iyo" S. Pimentel (16 February 1933 – 26 June 2017) was a Venezuelan international tennis player.

In 1955 whilst on tour in Great Britain he won his first singles title at the Worcestershire Championships on grass against Arsenio Motolko.

In 1956 he won the singles title at the Santander International in Spain against Juan Manuel Couder.

In 1958 he won the singles title at the Hoylake and West Kirby Open in England against Roy Stilwell.

In 1971 he won his final singles title at the Centro Italiano-Venezolano Championship against Ismael Sauce.