State Highway 73 (abbreviated SH-73 or OK-73) is a 24½ mi[1] (39.4 km) state highway mostly in Custer Co., Oklahoma, although a stretch of about four-fifths of a mile (1.3 km) of its eastbound lane lies in Roger Mills Co. SH-73 has no lettered spur routes.

The western terminus of the highway occurs at a jog in the Roger Mills–Custer county line; north of the intersection, SH-34 runs along the north–south boundary, and at the intersection, the boundary makes a ninety-degree turn to head east–west.

SH-73 serves the southwestern portion of the lake, and runs along the edges of Foss State Park.

SH-44/73 travel together for 2 miles (3.2 km)[3] before SH-73 splits off, returning to a due east course.

West of Clinton, the highway crosses a set of railroad tracks at the unincorporated locale of Ralph.