Pornassio () is a comune (municipality) in the Province of Imperia in the Italian region Liguria, located about southwest of Genoa and about northwest of Imperia. As of 31 December 2004, it had a population of 642 and an area of .
Pornassio borders the following municipalities: Armo, Cosio di Arroscia, Montegrosso Pian Latte, Ormea, Pieve di Teco, and Rezzo.