The 1998 Western Illinois Leathernecks football team represented Western Illinois University as a member of the Gateway Football Conference during the 1998 NCAA Division I-AA football season. They were led by ninth-year head coach Randy Ball and played their home games at Hanson Field. The Leathernecks finished the season with an 11–3 record overall and a 5–1 record in conference play, making them conference champions. The team received an automatic bid to the NCAA Division I-AA Football Championship playoffs, where they defeated Montana and Florida A&M before losing to Georgia Southern in the semifinals. The team was ranked No. 4 in The Sports Network's postseason ranking of Division I-AA.