| One South Dearborn | |
| Location: | 1 S. Dearborn St. Chicago, Illinois United States |
| Coordinates: | 41.8817°N -87.6286°W |
| Start Date: | 2003 |
| Completion Date: | 2005 |
| Building Type: | Office |
| Roof: | 571feet |
| Top Floor: | 502feet |
| Floor Count: | 39 |
| Elevator Count: | 19 |
| Floor Area: | 249326m2 |
| Architect: | DeStefano Keating Partners |
| Structural Engineer: | Halvorson and Partners |
| Current Tenants: | Sidley Austin LLP |
| Main Contractor: | Turner Construction Company |
| Developer: | Hines |
One South Dearborn is a 571 ft (174m) tall skyscraper in Chicago, Illinois. An earlier proposal for the same site proposed a much taller 112-story building. The current anchor tenant is Sidley Austin LLP, which moved into One South Dearborn in November 2005 from Bank One Plaza.[1]