Chachani is a volcanic group in southern Peru, 22 kilometres (14 mi) northwest of the city of Arequipa. Part of the Central Volcanic Zone of the Andes, it is 6,057 metres (19,872 ft) above sea level. It consists of several lava domes and individual volcanoes such as Nocarane, along with lava shields such as the Airport Domes. Underneath Chachani lies a caldera.

During the Pliocene and early Pleistocene, the volcanic group produced large ignimbrites such as the La Joya, Arequipa Airport, and Yura Tuff ignimbrites; afterwards, the volcanic group proper grew in the caldera until about 56,500 years ago. There have been no eruptions during historical times. Still, the volcano is considered to be only dormant, and due to its closeness to the city of Arequipa, it is considered high-risk.

The name means "brave" in Aymara or "mountain of man"/"mountain of male"; the alternative spellings "Cacheni" and "Charchani" are also known.

The volcano lies in the Andes of southern Peru, 22 kilometres (14 mi) northwest of Arequipa and north of the Arequipa Airport; the city of Arequipa is situated on the foot of Chachani and El Misti volcanoes. The road from Arequipa to Chivay runs along the southeastern foot of Chachani, and a dirt road reaches to an elevation of 5,000 metres (16,000 ft). It is considered to be one of the most easily climbed mountains in the 6,000–7,000 m range, although acclimatization and good physical health are required to ascend it. In the late 19th century, the good sight from Chachani was remarked upon. Politically, it lies in the Cayma, Yura, and Cerro Colorado districts.

Volcanoes in the southern part of Peru include from north to south Auquihuato, Firura, Coropuna, Andagua volcanic field, Sabancaya, Ampato, Chachani, El Misti, Pichu Pichu, Ubinas which has erupted intermittently since 1954, Huaynaputina where a large eruption occurred in 1600, Ticsani, Tutupaca, Yucamane, and Casiri. Some of these volcanoes are among the highest in the world,, and on average, there is one eruption of a Peruvian volcano every 13 years. The Peruvian volcanoes are part of the Central Volcanic Zone of the Andes, one of three separate volcanic belts in that mountain chain; the Central Volcanic Zone contains 44 named stratovolcanoes.

Chachani is an about 2-kilometre-high (1.2 mi) and 17-kilometre-wide (11 mi) complex of lava domes, stratovolcanoes, and volcanic cones; the highest summit is 6,057 metres (19,872 ft) high, making Chachani the 84th-highest peak in the Andes. The Chachani complex has an arcuate shape encompassing both the main Chachani volcano and the 5,784-metre-high (18,976 ft) Nocarane to the north of Chachani, while the 5,484-metre-high (17,992 ft) La Horqueta together with El Rodado to its west and Chachani proper to its east forms an east–west-trending ridge. La Horqueta has a young appearance and resembles an ash cone with a crater. Additional peaks are the northerly 5,852-metre-high (19,199 ft) high los Ángeles and the southeasterly 5,820-metre-high (19,090 ft) Trigo. In total, Chachani is made up of more than 12 edifices.

The Colorado lava domes which are also known as Cerro Penones in turn are located northwest from Nocarane. To the south of Chachani lie the Airport Domes, an 8-kilometre-wide (5.0 mi) lava shield with two discernible vents and a pristine appearance. The lava shield consists of overlapping lava flows with a wavy and rugose texture and a steep front which reaches heights of 1.2 kilometres (0.75 mi); evidently these were formed by viscous lava flows. A volcanic caldera associated with widespread ignimbrites in the Arequipa area may be located underneath Chachani; to the north its outline is marked by a 20-kilometre-wide (12 mi) amphitheatre while its southern part is continuous with the Arequipa depression and is generally poorly recognizable. The El Misti volcano later arose on the margin of the Chachani caldera, where it intersects the border of the Altiplano.

The volcanic complex is formed mainly by aa and block lava flows that rarely reach lengths of about 10 kilometres (6.2 mi); additionally, pyroclastic flows and tephra occur. The volcanic complex covers an area of about 600 square kilometres (230 sq mi) and has a present-day volume of about 154–248 cubic kilometres (37–59 cu mi); this makes Chachani one of the largest volcanoes of the Andes. Glacial erosion and landslides have affected the volcanic complex, forming cirques and U-shaped valleys and removing much of the original shape of the individual volcanoes. Some moraines have been overrun by lava flows.