| Lock and Dam No. 5A | |
| Location Map: | Wisconsin |
| Dam Crosses: | Upper Mississippi River |
| Res Name: | Pool 5A |
| Location: | Buffalo County, Wisconsin / Winona County, Minnesota, United States. Near Fountain City, Wisconsin. |
| Operator: | U.S. Army Corps of Engineers, St. Paul District |
| Dam Length: | 682feet(movable portion) |
| Opening: | June |
| Res Capacity Total: | 39600acre feet |
| Res Catchment: | 59105mi2 |
| Coordinates: | 44.0851°N -91.6737°W |
Lock and Dam No. 5A is a lock and dam located near Fountain City, Wisconsin and Goodview, Minnesota on the Upper Mississippi River around river mile 728.5.
It was constructed in 1932, placed in operation in 1936. Its last major rehabilitation was from 1989 through 2000.
The dam consists of a concrete structure 682feet long with five roller gates and five tainter gates with an earth embankment 22000feet long. Its concrete overflow spillway is 1000feet long and its lock is 110feet wide by 600feet long.
The lock and dam are owned and operated by the St. Paul District of the United States Army Corps of Engineers-Mississippi Valley Division.