Nichinan is located in the southern part of Miyazaki Prefecture on Japan's southernmost main island, Kyūshū.

The domain was noted for the quality of its han school, one of whose graduates was the Meiji period diplomat Marquis Komura Jutarō.

The town of Aburatsu and the villages of Agata, Obi, Hosoda, Nangō and Tōgō were established on May 1, 1889 with the creation of the modern municipalities system.

On January 1, 1950, the city of Nichinan was established through an amalgamation of the towns of Agata, Aburatsu, and Obi, and the village of Tōgō.

Aburatsu's increasing role as a harbor has made it a regular stopover for both domestic and foreign ships,[citation needed] and it is becoming an authentic international trading port.

[citation needed] On August 8, 2024 at 16:22 JST, the 7.1 Mw 2024 Hyūga-nada earthquake struck in the Hyūga Sea off the coast of Miyazaki Prefecture, Kyushu, Japan, 20 km (12 mi) northeast of Nichinan.

[6] Nichinan has a mayor-council form of government with a directly elected mayor and a unicameral city council of 19 members.

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

Mandarin oranges, ponkan, sweet peas, green peppers, kumquats, and rice are the main agricultural products of Nichinan.

There are three major yearly festivals in Nichinan: Other events include spring and autumn training for the Hiroshima Carp baseball team, swimming and marathon events, and monthly morning markets held at Aburatsu port and in front of Nichinan City Hall.