1991 Marshall Thundering Herd football team

The 1991 Marshall Thundering Herd football team represented Marshall University as a member of the Southern Conference (SoCon) during the 1991 NCAA Division I-AA football season. Led by second-year head coach Jim Donnan, the Thundering Herd compiled an overall record of 11–4 with a mark of 5–2 in conference play, tying for second place in the SoCon. Marshall advanced to the NCAA Division I-AA Championship playoffs, where they beat Western Illinois in the first round, Northern Iowa in the quarterfinals, and Eastern Kentucky in the semifinals before losing to Youngstown State in the NCAA Division I-AA Championship Game.

Marshall played home games in the newly-opened Marshall University Stadium in Huntington, West Virginia.