Chainat is located on the east bank of the Chao Phraya River. The community was moved from the old site at Sankhaburi in the reign of King Rama IV. Chainat was an important town used several times as a base to confront the Burmese army. Every time, the Burmese were defeated, thus originating the name of Chainat which means a place of victory.

Chainat occupies an area of 2,469 square kilometres and is administratively divided into 6 districts: Amphoe Muang Chai Nat, Amphoe Hankha, Amphoe Manorom, Amphoe Sankhaburi, Amphoe Sapphaya, Amphoe Wat Sing, and 2 sub-districts: King Amphoe Nong Mamong and King Amphoe Noen Kham.