Barnum is an unincorporated place in the southwestern part of Johnson County in north-central Wyoming, United States.

Barnum is at the western terminus of Wyoming Highway 190, approximately 17 miles west of the Kaycee exit off Interstate 25 (with U.S. Route 87).

[3] Mayoworth is several miles north of Barnum, and Big Trails is the nearest place over the Bighorn range.

[4] The Middle Fork of the Powder River Recreation Area provides access to canyonlands, hiking, and fishing.

[5] Nearby Dull Knife Battlefield is the site of an 1876 battle between the U.S. Army and Cheyenne.