| Bültsee (Dan. Bulsø) | |
| Pushpin Map: | Schleswig-Holstein |
| Location: | Rendsburg-Eckernförde, Schleswig-Holstein |
| Coords: | 54.4956°N 9.7543°W |
| Basin Countries: | Germany |
| Area: | 20.1ha |
| Max-Depth: | 43.96feet |
| Elevation: | 30.68order=flipNaNorder=flip |
Bültsee (da|Bulsø) is a lake in Rendsburg-Eckernförde, Schleswig-Holstein, Germany. At an elevation of 30.68order=flipNaNorder=flip, its surface area is 0.078 square miles (20.10 ha).
The name of the lake is first noted around 1600. The name derives from Old Danish bolt in the meaning round increase (cf. indoeuropean. *bhel≈to swell, to bubble, to be round).[1]