Christchurch is the largest city in the South Island and the second-largest city by urban area population in New Zealand, after Auckland. Christchurch lies in the Canterbury Region, near the centre of the east coast of the South Island, east of the Canterbury Plains. It is located near the southern end of Pegasus Bay, and is bounded to the east by the Pacific Ocean and to the south by Banks Peninsula. The Avon River / Ōtākaro flows through the centre of the city, with a large urban park along its banks. Christchurch has a reputation for being an 'English' city, with its architectural identity and common nickname the "Garden City" due to similarities with garden cities in England.

The South Island, also named Te Waipounamu in Māori, is the larger of the two major islands of New Zealand in surface area, the other being the smaller but more populous North Island. It is bordered to the north by Cook Strait, to the west by the Tasman Sea, and to the south and east by the Pacific Ocean. The South Island covers 150,437 square kilometres (58,084 sq mi), making it the world's 12th-largest island, constituting 56% of New Zealand's land area. At low altitude, it has an oceanic climate.