Apennines, mountain chain in Italy, extending from the Ligurian Alps in the north-west through the length of the Italian Peninsula to the Strait of Messina and into Sicily. The chain is a branch of the Alpine system and consists of eight ranges, including the Lucanian, Tuscan, Umbrian, and Calabrian. The chain, generally uniform in appearance, is about 1,290 km (800 mi) long and up to 129 km (80 mi) wide. Although the highest peaks include Monte Corno (2,912 m/9,554 ft) and Mount Amaro (2,795 m/9,170 ft), the average elevation is about 1,220 m (4,000 ft) above sea level. Two active volcanoes, Mount Vesuvius (1,277 m/4,190 ft) near Naples and Mount Etna (3,323 m/10,902 ft) in Sicily, are part of the Apennine system.

The eastern side of the chain is the source of streams that are generally short and small, of which the only important river is the Ofanto in south-eastern Italy. The western slopes give rise to several important rivers (Arno, Tiber, Volturno, Garigliano) and have some hydroelectric stations. The central and northern divisions of the chain contain valuable deposits of iron ore, copper, tin, mercury, lignite, and borax. The famous quarries of Carrara marble are located in the north-western part of the system.

Over the centuries the middle and lower slopes of the Apennines were cleared of forests, but a process of reforestation is now slowly progressing. Chestnut, birch, oak, and pine trees grow at altitudes of up to 1,800 m (6,000 ft), but above the tree line, vegetation consists mainly of shrubs and grasses that are sometimes used for pastureland. The hills and plateau areas support extensive olive groves, vineyards, orchard and nut trees, and pastures.