The Illinois Thunder were an indoor soccer club (based in Rockford, Illinois) that competed in the National Professional Soccer League.
After the 1991/92 season, the team became the Denver Thunder.
| Year | Division | League | Reg. Season | Playoffs | Avg. Attendance |
|---|---|---|---|---|---|
| 1990/91 | N/A | NPSL | 4th, National | Did not qualify | 1,613 |
| 1991/92 | N/A | NPSL | 3rd, National | Quarterfinals | 2,160 |