Nahari is located in southeastern Kōchi Prefecture on the island of Shikoku, with a coastline the Pacific Ocean to the southwest.

Kōchi Prefecture Nahari has a humid subtropical climate (Köppen Cfa) characterized by warm summers and cool winters with light snowfall.

During the Edo period, the area was part of the holdings of Tosa Domain ruled by the Yamauchi clan from their seat at Kōchi Castle.

Nahari has a mayor-council form of government with a directly elected mayor and a unicameral town council of ten members.

In terms of national politics, the town is part of Kōchi 1st district of the lower house of the Diet of Japan.