Tahanea Atoll is quite large. It measures 48 km in length with a maximum width of 15.2 km. The southern reef fringing the atoll is wider than the northern one, but the largest islands are on the narrower northern rim. Tahanea has a wide and deep lagoon with a surface of 545 km². There are three deep, navigable, passes into the lagoon, which are called Motupuapua, Teavatapu and Otao.
Tahanea is uninhabited, but it is visited occasionally by islanders from neighboring atolls.