Dugi otok (pronounced [dûɡiː ǒtok]; Croatian for “Long Island”, Italian: Isola Lunga) is the seventh largest island in the Adriatic Sea, part of Croatia. It is located off the Dalmatian coast, west of Zadar. It is the largest and eastern-most of the Zadarian Islands, and derives its name from its distinctive shape (it is 45 km long by 5 km wide with an area of 114 km²). Its elevation reaches 300 m; and many of its higher portions contain stands of Maritime Pine.

The western coast is tall and rugged, and many of the towns are clustered on the eastern side, including Sali, the largest, Božava, Dragove, Soline, Brbinj, Luka, Polje, Verona, Savar, Veli Rat, Zaglav, and Žman. A nature park, Telašćica, covers the southern part of the island and is adjacent to Kornati Islands National Park.

The island has been inhabited since prehistoric times. The Byzantine Emperor Constantine VII in the 10th century mentioned it under the name of Pizuh, and later it was called Insula Tilagus in documents ("pelagos"in Greek means sea), and its Latin name was Insula maior. In the 15th century it was registered as Veli otok.

Otok is a town in eastern Croatia, located 20 km south of Vinkovci, in eastern Slavonia. The population of the town of Otok is 6,366 (census 2011), with 4,720 residents in Otok itself and 1,646 in the nearby village of Komletinci. In the census of 2001, 98.98% of the population declared themselves Croats.