Tutupaca is a volcano in the region of Tacna in Peru. It is part of the Peruvian segment of the Central Volcanic Zone, one of several volcanic belts in the Andes. Tutupaca consists of three overlapping volcanoes formed by lava flows and lava domes made out of andesite and dacite, which grew on top of older volcanic rocks. The highest of these is usually reported to be 5,815 metres (19,078 ft) tall and was glaciated in the past.

Several volcanoes in Peru have been active in recent times, including Tutupaca. Their volcanism is caused by the subduction of the Nazca Plate beneath the South America Plate. One of these volcanoes collapsed in historical time, probably in 1802, generating a large debris avalanche with a volume likely exceeding 0.6–0.8 cubic kilometres (0.14–0.19 cu mi) and a pyroclastic flow. The associated eruption was among the largest in Peru for which there are historical records. The volcano became active about 700,000 years ago, and activity continued into the Holocene, but whether there were historical eruptions was initially unclear; some eruptions were instead attributed to the less eroded Yucamane volcano. The Peruvian government plans to monitor the volcano for future activity. Tutupaca features geothermal manifestations with fumaroles and hot springs.

The people in Candarave considered Tutupaca to be a "bad" mountain, while Yucamane was the "good" one; this may reflect that Tutupaca had recent volcanic eruptions. The Peruvian geographer Mateo Paz Soldán dedicated an ode to Tutupaca.

Tutupaca is 25–30 kilometres (16–19 mi) north of the town of Candarave in the region of Tacna in Peru. Lake Suches lies north of the volcano, and two rivers flow nearby: the Callazas River, flowing eastward to the north of the volcano, and then southward past Tutupaca's eastern flank, and the Tacalaya River, which flows south along Tutupaca's western flank. The local climate is cold, and the terrain is stony, with little vegetation. During the wet season, the mountain is snow-covered, and meltwater from Tutupaca and other regional mountains is an important source of water for the rivers in the region. In contrast, the volcano itself is largely unaffected by human activity.

Tutupaca consists of two volcanic complexes: an older complex that is highly eroded, and two northerly peaks which formed more recently. Of these, the eastern peak ("eastern Tutupaca") consists of seven presumably Holocene lava domes and is 5,790 metres (19,000 ft) high, while the western one ("western Tutupaca") consists of lava domes, lava flows and Plinian eruption deposits of Pleistocene age, and reaches a height of 5,815 metres (19,078 ft). The Global Volcanism Program gives heights of 5,753 metres (18,875 ft) for the eastern and 5,801 metres (19,032 ft) for the western summit. The western peak is the highest summit of Tutupaca.

The base that Tutupaca rises from lies at elevations ranging from 4,400 metres (14,400 ft) to 4,600 metres (15,100 ft) and the volcano covers a surface area of about 150–170 square kilometres (58–66 sq mi). The older complex is formed mainly by lava flows, which during the Pleistocene were eroded by glaciers forming up to 100 metres (330 ft) thick moraines and U-shaped glacial valleys. Cirques and moraines are also found on the western summit, and tephra layers extend west of the volcano. The older complex, which includes lava domes in the form of small hills on its southern part, was the source of ignimbrite that covers the western and southern parts of the volcano. Postglacial lava flows emanating from a vent located between the two peaks have been identified. Proglacial processes like frost shattering have altered young volcanic products.

The older complex and western Tutupaca have erupted andesite and dacite, while eastern Tutupaca has only produced dacite. Trachyandesite and trachyte also occur. The volcanic rocks erupted during the Holocene define a potassium-rich calc-alkaline suite. Dacites from eastern Tutupaca contain amphibole, apatite, biotite, clinopyroxene, iron-titanium oxides, orthopyroxene, plagioclase, quartz, and sphene. Mafic rock fragments are rarely found embedded in Tutupaca rocks. The basal volcanic rocks have suffered hydrothermal alteration, forming clays. Elemental sulfur deposits have been identified at Tutupaca and a 1996 map of the volcano shows a sulfur mine on its southeastern flank.

A 1 kilometre (0.62 mi) wide amphitheater in eastern Tutupaca, open to the northeast, was formed by a major collapse of the volcano. Lava domes from the younger Tutupaca, as well as highly altered lavas from the older complex, are exposed within the collapse scar, which is the origin of a 6–8-kilometre (3.7–5.0 mi) long debris avalanche deposit. The deposit is mostly found within glacial valleys and is interlaid by the Paipatja pyroclastic flow which divides the debris into two units. The pyroclastic flow reaches both Lake Suches north of the volcano and the Callazas River east of it.