The town of Tapanui lies in West Otago in New Zealand's South Island, close to the boundary with Southland region. A forestry town, it lies between the foot of the Blue Mountains and the Pomahaka River.

In New Zealand the name Tapanui is closely associated with the mysterious ailment chronic fatigue syndrome, which - until it became an accepted ailment - rejoiced in the nickname of "Tapanui 'flu". The doctor who first documented the rise of the condition in New Zealand was based in the town.