| Lock and Dam No. 4 | |
| Location Map: | Wisconsin |
| Dam Crosses: | Upper Mississippi River |
| Res Name: | Pool 4 |
| Location: | Alma, Buffalo County, Wisconsin / Greenfield Township, Wabasha County, Minnesota, United States. |
| Operator: | U.S. Army Corps of Engineers, St. Paul District |
| Dam Length: | 1367feet (movable portion) |
| Opening: | May |
| Res Capacity Total: | 878000acre feet |
| Res Catchment: | 57100mi2 |
| Coordinates: | 44.3256°N -91.9203°W |
Lock and Dam No. 4 is a lock and dam located near Alma, Wisconsin and Kellogg, Minnesota on the Upper Mississippi River around river mile 752.8. The lock and dam are owned and operated by the St. Paul District of the United States Army Corps of Engineers-Mississippi Valley Division.
The lock and dam was constructed and placed in operation in May 1935. There were ten major injuries and three deaths recorded during construction of the facility. Its last major rehabilitation was from 1988 to 1994.