Fukuoka Prefecture Onga has a humid subtropical climate (Köppen Cfa) characterized by warm summers and cool winters with light to no snowfall.

About 3000 years ago, the large Ko-Onga Bay covered the area where the town of Ong now lies.

After the Meiji restoration, the villages of Shimamon and Asaki were established on May 1, 1889 with the creation of the modern municipalities system.

Onga has a mayor-council form of government with a directly elected mayor and a unicameral town council of 13 members.

In terms of national politics, the town is part of the Fukuoka 8th district of the lower house of the Diet of Japan.