Lake Waahi (or up to 1913 sometimes called Lake Waihi)[1] is located immediately to the west of Huntly, in the Waikato Region.

[2] Lake Waahi is a riverine lake, which links to the Waikato River by way of the short Waahi Stream.

[3] The smaller Lake Puketirini lies immediately to Waahi's southeast.

The lake has a maximum depth of five metres and the open water covers approximately 522 hectares,[2] though the lake extends further through marsh and fenland.

The lake is situated within predominantly pastoral land.