Waitaha is an early historical Māori iwi. Inhabitants of the South Island of New Zealand, they were largely absorbed via marriage and conquest first by the Kāti Mamoe and then Ngāi Tahu from the 1500s onward.
Today those of Waitaha descent are represented by the Ngāi Tahu iwi[1].
Another iwi known as Waitaha lived in the Horowhenua area of the lower North Island.

"Nation of Waitaha"
A number of organisations have "Waitaha" as part of their title, often in a generic "ancient links to the land" sense, or as a synonym for Canterbury rather than either claiming actual tribal descent, or links to the philosophies of Brailsford. These include:

Waitaha Scout Group, based in Dunedin, Otago
Waitaha Cultural Council, Christchurch-based performance group
Canterbury/Waitaha District Council of the NZEI