A new species of tetraploid cotton, Gossypium caicoense, Condorcet, Hermógenes et Imre, is described. It was collected as a wild component of the natural vegetation in the "Serra da Formiga", near Caicó, State of Rio Grande do Norte, Brazil, by research workers of the Cotton Section of the "Instituto Agronômico do Estado de São Paulo", in September of 1963. Its chromosome number is 2n = 52. It was cultivated and studied in greenhouse conditions at the referred Institute and showed significant morphological differences when compared to the known tetraploid species of the Genus as well as to existing descriptions of Brazilian native types of cotton. A discussion of the data obtained by a comparative study establishes the main morphological differences between G. caicoense and the cultivated species G. hirsutum and G. barbadense var. brasiliense.