The 2021 Southern Utah Thunderbirds football team represented Southern Utah University in the 2021 NCAA Division I FCS football season.

They were led by sixth-year head coach Demario Warren and played their home games at Eccles Coliseum in Cedar City, Utah.

They played their final season as a member of the Big Sky Conference, as they would depart for the Western Athletic Conference for the 2022 season.

On July 26, 2021, during the virtual Big Sky Kickoff, the Thundebirds were predicted to finish eleventh in the Big Sky by both the coaches and media.

[1] The Thunderbirds had one player selected to the preseason all-Big Sky team.