Rijeka (Italian Fiume), city in north-west Croatia, a seaport on the Gulf of Kvarner, an inlet of the Adriatic Sea. Its major industries include shipbuilding, oil refining, woodworking, metalworking, and the manufacture of machinery, chemicals, and tobacco and leather products. The castle of Tvsat and the cathedral, construction of which was begun in the late 14th century, are prominent landmarks in the city. The University of Rijeka (1873) is here.

In early times Rijeka was part of the Holy Roman Empire. In 1471 it became part of Austria, and in 1779 it was attached to Hungary. After World War I a dispute broke out between Italy and the Kingdom of the Serbs, Croats, and Slovenes (later Yugoslavia) over the disposition of Rijeka. During the peace conference of 1919, the Italian soldier-poet Gabriele D'Annunzio, at the head of a band of Italian legionaries, seized Rijeka. He and his men occupied the city until November 1920, when Rijeka was made a free state by the Treaty of Rapallo between Italy and the Yugoslav kingdom. A new treaty, signed at Rome in 1924, awarded the city and district to Italy, leaving the suburb of Sušak to the Yugoslavs. Rijeka remained under Italian control until 1945, when it was ceded by Yugoslav partisans. In 1947 Rijeka was formally ceded to Yugoslavia. In 1991 Croatia, once a constituent republic of Yugoslavia, declared its independence. Population 143,395 (2001).