The morphology and histology of the ovary is investigated in four species representing the four genera of the family Costaceae. Only one species of Costus has been investigated prior to this study. The present study identifies new characters and confirms or corrects those previously reported for all four genera. Aspects of ovary structure studied include the general topography and histology of the ovary, paths of the stylar canals, the prolongation of the ovary above the locules, the presence of a vascular plexus at the top of the ovary, and the position and structure of the floral nectary. These characters contribute to a broader data base for phylogenetic analysis of the Zingiberales.