Udon Thani is a province (changwat) in northeast Thailand. It is bordered by the provinces of Nong Khai to the north, Sakon Nakhon to the east, Kalasin Province to the southeast, Khon Kaen to the south, and Loei and Nong Bua Lam Phu Province to the west. It occupies an area of 11,730 km². The provincial capital is Udon Thani, the major city in the province.