Oak Mountain is a 1,631-foot summit in the southwestern corner of St. Francois County, Missouri, on a north-south ridge extending into Iron County. Near Pilot Knob, with Middlebrook to the northwest and Iron Mountain Lake to the north, it also includes the source area of Knob Creek on its western flank. The mountain was named for the oak trees growing there and was also known by the variant name Buzzard Mountain.