Rovinj , Ital. Rovigno d'Istria, town (1991 pop. 12,910), in Croatia, on the Istrian coast of the Adriatic Sea. It is a seaport with shipbuilding and fishing industries. Rovinj belonged to Venice from 1283 until 1797, when it passed to Austria. Italy acquired it in 1918, and it was ceded to Croatia, then a constitute republic of Yugoslavia, in 1947. The town has an institute of marine biology and an 18th-century cathedral.