| Bridge Name: | St. Charles Air Line Bridge |
| Official Name: | St. Charles Air Line Bridge |
| Carries: | 2 tracks of the Canadian National Railway |
| Crosses: | Chicago River (south branch) |
| Locale: | Chicago, Illinois |
| Maint: | Canadian National Railway |
| Design: | Strauss Trunnion bascule lift span |
| Designer: | Joseph Strauss |
| Mainspan: | Originally 260feet, later shortened to 220feet in 1930 |
| Open: | 1919 |
The St. Charles Air Line Bridge is a Strauss Trunnion bascule bridge which spans the Chicago River in Chicago, Illinois.
Built as part of the St. Charles Air Line Railroad by the American Bridge Company in 1919, the bridge originally had a span of 260feet. This bridge held the world record for longest bascule-type span until 1930, when it was shortened to 220feet during a relocation as a result of straightening the river channel. The chief design engineer of the original bridge was Leonard O. Hopkins.