Tapanui is a picturesque town in West Otago in New Zealand's South Island, close to the boundary with Southland region (population 744 as of 2006 census). A forestry town, it lies between the foot of the Blue Mountains and the Pomahaka River. Deer stalking and trout fishing are popular pastimes of the area. For almost a hundred years, the town was serviced by the Tapanui Branch railway line, which despite its name never actually terminated in Tapanui. This line was formally opened in late 1880 and closed after being damaged by severe flooding in the region in October 1978.
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, Dr Peter Snow, was based in the town.
Landslip Hill is a nearby fossil-bearing geological feature. Tapanui has a school that leads up to year 13 called Blue Mountain College.