U Thong (Thai: อู่ทอง, pronounced [ʔùː tʰɔ̄ːŋ]) is the district (amphoe) in the western part of Suphan Buri province, north of Bangkok.

Radiocarbon determinations from the sites of U-Thong and Chansen suggest that the transition into complex state societies in the Chao Phraya basin took place between about 300-600 AD."

A copper inscription from the mid-7th century states, "Sri Harshavarman, grandson of Ishanavarman, having expanded his sphere of glory, obtained the lion throne through regular succession," and mentions gifts to a linga.

[4] In 1944, the government moved the centre of the district from Ban Chorakhe Sam Phan to the area of the ancient city.

[5] Neighbouring districts are (from the north clockwise): Don Chedi, Mueang Suphan Buri, Bang Pla Ma, Song Phi Nong of Suphan Buri Province; Lao Khwan, Huai Krachao, and Phanom Thuan of Kanchanaburi province.