island in the Adriatic Sea forming the northernmost part of Dalmatia in Croatia. It reaches a maximum altitude of 1,339 ft (408 m) at Mt. Kamenjak and comprises three ridges of limestone. Over 300 freshwater springs provide a valuable water supply to the population of the island—which, in contrast to most of the Adriatic islands, is increasing, in part because of good communications with the mainland. After its initial settlement as the colony of Arba by prehistoric Illyrians, Rab successively came under Greek, Roman, Croatian, Venetian, Austrian, French, Italian, Yugoslavian, and again Croatian rule, reflecting the historic fluctuations of power in the Adriatic.

The principal town, Rab, is one of the most popular resorts of Croatia, a walled town with three parallel main streets built on a steep promontory along the west coast. At the south end is a 13th-century Romanesque cathedral, whose campanile is considered the finest example of Romanesque architecture on the Adriatic littoral. It is the first in a line of four bell towers on a ridge dominating the old town. There are several historically interesting houses built by patrician Venetian families. Six hamlets are supported by fishing, agriculture, tourism, and a ready-made clothing enterprise. Area 35 square miles (91 square km). Pop. (2001) town, 554.