U Thong District (Thai: อู่ทอง, pronounced [ʔùː tʰɔ̄ːŋ]) is the district (amphoe) in the western part of Suphan Buri Province, north of Bangkok.
Higham states, "U-Thong was occupied for many centuries prior to the development of the Dvaravati state. 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. The site includes a moat, 1,690 by 840 m, and the Pra Paton caitya.