| Längsee | |
| Location: | Carinthia, Austria |
| Coordinates: | 46.7894°N 14.4242°W |
| Type: | lake |
| Pushpin Map: | Austria |
| Pushpin Map Alt: | Location of Längsee in Austria. |
Längsee is a lake of Carinthia, Austria. It is the name affix of the town Sankt Georgen am Längsee.