Rab (räb), Ital. Arbe, island, 40 sq mi (104 sq km) off Croatia, in the Adriatic Sea. One of the Dalmatian islands, it is a popular seaside resort. Fishing and agriculture are the main occupations. The island was under Venetian rule from the 10th cent. until 1797, and it retains its ancient walls, the ruins of the palace of the Venetian governors, a 12th-century cathedral, and the medieval palace of the former archbishops.