city, capital of Enna provincia (province), central Sicily, Italy, on a plateau dominating the valley of the Dittaino, northeast of Caltanissetta. A city of the Siculi, an ancient Sicilian tribe, and a centre of the pre-Hellenic cult of Demeter and Kore (Persephone), it originated as Henna and early came under Greek influence, first from Gela (7th century BC) and later from Syracuse, after which it fell into the hands of the Syracusan tyrant Dionysius I in about 397 BC. After a brief period (4th century) of Carthaginian rule, it passed to the Romans in 258 BC. It was the headquarters (134–132 BC) of the great Sicilian slave revolt. It was of little note in later classical times, but its natural strength and strategic position gave it renewed importance in the Middle Ages. Held by the Saracens from 859 until 1087, it was then taken by the Normans. Its medieval name Castrogiovanni, derived from the Arabic Kasr-Yani, is a corruption of the Latin Castrum Hennae. A favourite residence of the emperor Frederick II of Hohenstaufen and of Frederick II and III of Aragon, it was among the first Sicilian cities to rally to the Italian cause in 1848 and 1860. In 1927 it resumed its ancient name.

Notable buildings include an octagonal tower of Emperor Frederick II, the cathedral (1307; rebuilt in Baroque style), and the Castello di Lombardia, the work of many periods. The Lago (lake) di Pergusa, 4 miles (6 km) south, is the traditional scene of the seizure of Persephone (Proserpina) by Hades (Pluto), king of the underworld.

An episcopal see, the city is a summer resort and agricultural centre. Sulfur is mined in the vicinity. Pop. (2004 est.) 28,625.