Sumner is a coastal seaside suburb of Christchurch, New Zealand and was surveyed and named in 1849 in honour of John Bird Sumner, the then newly appointed Archbishop of Canterbury and president of the Canterbury Association. Originally a separate borough, it was amalgamated with the city of Christchurch as communications improved and the economies of scale made small town boroughs uneconomic to operate.

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.