Vesuvius (Italian, Vesuvio, from Oscan word fesf,”smoke”), volcano in southern Italy, near the shore of the Bay of Naples and the city of Naples. It is the only active volcano on the European mainland. A solitary mountain rising from the plain of Campania, it has a base about 48 km (30 mi) in circumference and is surmounted by two summits, of which the higher is the cone known as Vesuvius proper. On August 24, ad 79, a great eruption of Vesuvius began; the top of the mountain was blown off by an explosion, and the cities of Herculaneum, Pompeii, and Stabiae were overwhelmed by a rain of ashes and mud. About 2,000 people were killed. No lava was ejected in this or any subsequent eruption until 1066.

An eruption in 1631 destroyed five towns and caused the deaths of more than 3,000 people. In 1794 a violent outbreak destroyed the town of Torre del Greco. Following numerous smaller outbreaks, a violent eruption took place in April 1906, lasting ten days and causing great destruction and the loss of 2,000 lives. Since then smaller outbreaks have occurred in 1913, 1926, 1929, and 1944.

The height of Vesuvius is 1,277 m (4,190 ft), while that of Monte Somma, the lesser summit, is 1,132 m (3,714 ft). The volcano's slopes are covered with vineyards and orchards. Higher up, oak and chestnut grow. A funicular railway has been constructed from the base of the cinder cone to the summit close to the edge of the crater, and an observatory is maintained near the crater.