Situated in West-Central Oklahoma, Canadian County is bounded by Kingfisher County on the north, Oklahoma and Cleveland counties on the east, Grady County on the south, Caddo County to the southwest, and Blaine County to the northwest. Canadian County lies mostly within the Red Bed Plains, a subregion of the Osage Plains physiographic region.
The county's northwestern corner is situated in the Gypsum Hills. Drained by the North Canadian and the Canadian rivers, which cross the county from northwest to southeast, the county consists of 905.17 square miles of land and water. In 2018 the incorporated towns included Calumet, Mustang, Okarche, Piedmont, Union City, Yukon, and El Reno (the county seat).