Trieste (city, Italy) (ancient Tergeste; Serbo-Croatian Trst), city and port, northeastern Italy, capital of Trieste Province and of Friuli-Venezia Giulia Region, on the Gulf of Trieste, at the northeastern extremity of the Adriatic Sea. Trieste has an excellent harbor and extensive freight-handling facilities. Industries include shipbuilding, petroleum refining, and the manufacture of iron and steel products, textiles, machinery, and foodstuffs. The old section of the city is on the lower slopes of San Giusto hill, and the modern section fronts on the harbor. Among the city landmarks are an amphitheater dating from Roman times and the Basilica di San Giusto (5th century). The University of Trieste (1938) is in the city, as is an institute for advanced study in physics (1979).

Trieste was built as a Roman port by the emperor Augustus in the 1st century bc. After the dissolution of the Western Roman Empire in the 5th century ad, it fell to Attila, king of the Huns; in the 6th century it passed to the Byzantine Empire. During the 8th century Trieste was ruled briefly by the Lombards of northern Italy and then passed to the Carolingian, or second, dynasty of Frankish kings. Later it became a free commune. In 1382 Trieste placed itself under the protection of Austria, maintaining that status except for two periods (1797-1805 and 1809-13), during which it was incorporated into French-dominated Italy, until after World War I. In 1719 the Holy Roman emperor Charles VI made Trieste a free port. With surrounding territory, it was constituted a separate crown land in 1867. The Austrian government revoked the free-port privileges of the city in 1891, authorizing instead a free trade zone. As the only Austrian seaport and a natural outlet for countries of central Europe, Trieste prospered throughout the 19th and early 20th centuries. Italian troops captured the city, long an Italian irredentist center, in 1918, during World War I. In 1919, by the terms of the Allied Treaty of Saint-Germain with Austria, the city, in which the Italian language and culture had long flourished, was assigned to Italy. Although the free trade zone was maintained, Trieste declined as a shipping center under Italian rule, because it was politically cut off from central Europe; industrial growth, however, continued. Yugoslav troops captured the city in May 1945, during World War II. By the terms of the peace signed (1947) by Italy after the war, Trieste and the surrounding area were made part of the Free Territory of Trieste, which was placed under the protection of the United Nations. The territory was divided into Zone A, which included the city of Trieste, and which was under Allied control, and Zone B, under Yugoslav control. Most of Zone A, including the city, was returned to Italian control under the provisions of an agreement between Italy and Yugoslavia, signed in 1954 and ratified by treaty in 1975, that allowed it to remain a free port. The rest of the territory was incorporated into Yugoslavia. It became part of Slovenia when the republic declared its independence in 1991. Population (2001) 211,184.