The Waitaki district, in the Canterbury and Otago regions of New Zealand, straddles the traditional border between the two regions, the Waitaki River. It has a land area of 7,151.94 km² , divided 59.28% to Canterbury Region and 40.72% to Otago Region. It is the only district in the South Island that is divided between two regions. A major reason for this split was the governance of the Waitaki River which forms a political boundary between Canterbury and Otago. With major hydro schemes on this river it was decided to place the entire catchment in one administrative region, thus forming the split.

The district, which is agricultural by nature, comprises the wide alluvial fan of the river, and runs inland along the banks of the river, this forming a roughly triangular region. The population is 21,000 (June 2013 estimate), Oamaru (in Otago) is the largest town in the district. The Waitaki District is made up of the former Waitaki County, Waihemo County and Oamaru Borough, which were amalgamated in 1989. It is governed by the Waitaki District Council. Gary Kircher is the District Mayor.

A relatively weakly settled area, the District does have a wide number of farms. However, in recent times (late 2000s), numerous proposals for new farming operations have locals fearing that the agriculture will be transformed from often family-held farms to large agribusiness operations causing increased local ecologic damage and siphoning off capital overseas.