The diversity of the genus Ulva in South American waters is matter of debate. Specimens of Ulva sp. were collected in northern Chile and analyzed using sequences of rbcL and tufA genes in combination with morphological observations. Molecular analyses revealed the presence of Ulva australis, a native species from northeast Asia that has also been recently recorded in southern Chile. Based on these results, an extension of the geographical distribution of U. australis toward northern Chile is reported.