Mount Etna, or simply Etna (Italian: Etna [ˈɛtna] or Mongibello [mondʒiˈbɛllo]; Sicilian: Muncibbeḍḍu [mʊntʃɪbˈbɛɖɖʊ] or a Muntagna; Latin: Aetna; Ancient Greek: Αἴτνα and Αἴτνη), is an active stratovolcano on the east coast of Sicily, Italy, in the Metropolitan City of Catania, between the cities of Messina and Catania. It lies above the convergent plate margin between the African Plate and the Eurasian Plate. It is one of the tallest active volcanoes in Europe, and the tallest peak in Italy south of the Alps with a current height (July 2021) of 3,357 m (11,014 ft), though this varies with summit eruptions. Over a six-month period in 2021, Etna erupted so much volcanic material that its height increased by approximately 100 ft (30 m), and the southeastern crater is now the tallest part of the volcano.

Etna covers an area of 1,190 km² (459 sq mi) with a basal circumference of 140 km (87 miles). This makes it by far the largest of the three active volcanoes in Italy, being about two and a half times the height of the next largest, Mount Vesuvius. Only Mount Teide on Tenerife in the Canary Islands surpasses it in the whole of the European–North-African region west of the Black Sea.

In Greek mythology, the deadly monster Typhon was trapped under this mountain by Zeus, the god of the sky and thunder and king of gods, and the forges of Hephaestus were said also to be underneath it.

Mount Etna is one of the world's most active volcanoes and is in an almost constant state of activity. The fertile volcanic soils support extensive agriculture, with vineyards and orchards spread across the lower slopes of the mountain and the broad Plain of Catania to the south. Due to its history of recent activity and nearby population, Mount Etna has been designated a Decade Volcano by the United Nations. In June 2013, it was added to the list of UNESCO World Heritage Sites.