Ulvales is an order of green algae in the class Ulvophyceae. Algae of this order are most commonly found in aquatic habitats (mainly marine or brackish waters); some are found in fresh water or are terrestrial. They are found free-floating, attached to a substrate, or endophytic.
The Ulvales consist of macroscopic or microscopic algae with diverse morphologies (filamentous, pseudoparenchymatous, tubular or blade-like). Cells generally contain a single parietally placed chloroplast with one or multiple pyrenoids, and one or multiple nuclei.