Lake Tekapo is the second-largest of three roughly parallel lakes running north–south along the northern edge of the Mackenzie Basin in the South Island of New Zealand (the others are Lake Pukaki and Lake Ohau). It covers an area of 83 square kilometres (32 sq mi), and is at an altitude of 700 metres (2,300 ft) above sea level.

The lake is fed at its northern end by the braided Godley River, which has its source in the Southern Alps to the north. The lake is a popular tourist destination, and several resort hotels are located at the township of Lake Tekapo at the lake's southern end. The Lake Tekapo Regional Park, administered by Environment Canterbury, is located on the southern shore of the lake.
An astronomical observatory is located at Mount John, which is to the north of the town, and south of the small Lake Alexandrina.