Fiesso Umbertiano is a comune (municipality) in the Province of Rovigo in the Italian region Veneto, located about southwest of Venice and about southwest of Rovigo. As of 31 December 2004, it had a population of 4,207 and an area of .
The municipality of Fiesso Umbertiano contains the frazioni (subdivisions, mainly villages and hamlets) Fornace Carotta, La Foscarina, Roncala, Capitello and Piacentina.
Fiesso Umbertiano borders the following municipalities: Canaro, Castelguglielmo, Frassinelle Polesine, Occhiobello, Pincara, Stienta.