200px|thumb|The former island of Ostrovo (map from 1912). Ostrvo or Ostrovo (meaning "island" in Serbian) was the largest Serbian river island on the Danube, with an area of . It was in length and in width. Today it is no longer an island but peninsula, which is connected to the southern bank of the Danube. Ostrvo lies east of Belgrade, near Kostolac, and is heavily forested. It has given its name to a village of Ostrovo in Kostolac municipality. The southern arm of Danube around Ostrvo is called Dunavac.