Uthai Thani (Thai: อุทัยธานี, pronounced [ʔù.tʰāj tʰāː.nīː]), one of Thailand's seventy-six provinces (changwat) lies in lower northern Thailand. Neighboring provinces are (from north clockwise) Nakhon Sawan, Chai Nat, Suphan Buri, Kanchanaburi and Tak. It lies somewhat off the route between Bangkok, 200 km distant and Chiang Mai.
The province stretches from the upper plains of the Chao Phraya River valley, to forested mountains in the west. The Sakae Krang River, a tributary of the Chao Phraya River, is the main watercourse of in the province.