This work reports the occurrence of the introduced alga Caulerpa ollivieri Dostál, 1929 in the Southern Gulf of Mexico off the northern coast of the Yucatan Peninsula, Mexico. In 2010, a specimen was collected off the Dzilam de Bravo, and additional specimens were detected in at least four localities along the coast. These records extend the distribution of C. ollivieri 800 km to the south; it was first recorded off the Tampa Bay in Florida (USA) in 1968 and subsequently in The Bahamas. Further work is now needed to determine the impact this introduced alga may have on the native benthic community.
