Tacora is a stratovolcano located in the Andes of the Arica y Parinacota Region of Chile. Near the border with Peru, it is one of the northernmost volcanoes of Chile. It is part of the Central Volcanic Zone in Chile, one of the four volcanic belts of the Andes. The Central Volcanic Zone has several of the highest volcanoes in the world. Tacora itself is a stratovolcano with a caldera and a crater. The youngest radiometric age is 50,000 years ago and it is heavily eroded by glacial activity.

Volcanism in the Central Volcanic Zone results from the subduction of the Nazca Plate beneath the South America Plate. Tacora is constructed on the so-called "Arica Altiplano" and is part of a north–south alignment of volcanoes. Tacora itself has uncertain reports of historical eruptions and there are active fumaroles.

The fumarolic activity has resulted in the emplacement of substantial deposits of sulfur, which were already mentioned centuries ago. Towards the latter 19th century, systematic mining of the sulfur deposits of Tacora occurred and substantial mining infrastructure was constructed on the mountain.

Tacora lies in the Arica y Parinacota Region of Chile, about 100 kilometres (62 mi) northeast of Arica. It is among the northernmost volcanoes of Chile and poorly known.

Tacora is part of the Central Volcanic Zone, one out of several volcanic belts of the Andes. The Central Volcanic Zone is one of the world's major volcanic provinces and features both a high density of volcanoes and some of the tallest volcanic edifices in the world. Volcanoes in the Central Volcanic Zone include Sabancaya, El Misti and Ubinas in Peru and Tacora, Isluga, Irruputuncu, Ollague, San Pedro, Putana, Alitar, Lascar and Lastarria in Chile, Bolivia and Argentina; there are about 34 volcanoes in the Chilean portion of the Central Volcanic Zone alone. Of these Lascar is considered to be the most active, with a large eruption in 1993. Aside from volcanoes, the Central Volcanic Zone also features geothermal fields such as El Tatio.

The volcano is a 5,980 metres (19,620 ft) high cone with a summit caldera that opens northwest and a 500-metre (1,600 ft) wide crater below the summit within the caldera scarp. Steep lava flows form the bulk of the edifice, along with lava domes and pyroclastic material, and rise about 1.7 kilometres (1.1 mi) above the surrounding terrain. The edifice is heavily eroded with about 32 metres (105 ft) of rocks gone but still has a circular shape. There are traces of a sector collapse scar and of the resulting debris avalanche on the southeastern flank.

According to some reports glaciers occur within the caldera at elevations above 5,500 metres (18,000 ft), while other reports indicate the absence of perennial snow on the mountain. Glacial valleys and moraines have been recognized on the eastern, southeastern and southern slopes of the volcano, and cirques have been found at 5,000 metres (16,000 ft) elevation. These landforms suggest that the mountain was formerly glaciated. Three sets of moraines have been described, one at 4,400 metres (14,400 ft) elevation possibly linked to the last glacial maximum, an older one at 4,500 metres (14,800 ft) elevation and a third at 4,900 metres (16,100 ft) elevation which may have formed during the Little Ice Age; moraines reach thicknesses of 200 metres (660 ft). There is an additional set of moraines at 4,350–4,300 metres (14,270–14,110 ft) elevation that has been correlated to pre-last glacial maximum glaciations, as well as traces of ice cored moraines and rock glaciers. Some rock glaciers still exist; unlike other glacial bodies in Chile the fronts of rock glaciers on Tacora are not retreating.

The mountain is an important source of water for the region. The Lluta River originates on Tacora, and its waters are highly salty owing to their origin on the volcano. The Chislluma River flows past the northeastern flank of Tacora and the Rio Caracarani past the southeastern one; finally, the Mauri Canal and Uchusuma Canal run along the southeastern slopes.