| Lake Siriu | |
| Location: | Romania |
| Coords: | 45.5°N 41°W |
| Type: | artificial lake |
| Inflow: | Buzău River |
| Pushpin Map: | Romania |
| Outflow: | Buzău River |
| Basin Countries: | Romania |
| Length: | 11.5km (07.1miles) |
| Area: | 420ha |
| Max-Depth: | 120m (390feet) (dam height) |
| Volume: | 155hm3 (max) |
| Cities: | Siriu |
Lake Siriu is an artificial dam lake in Romania, on the Buzău River valley. Construction of the dam started in 1982, and the 42 MW Nehoiașu hydroelectric plant was opened in 1994.
The dam is a high embankment dam with a clay core, the second largest embankment dam in Romania.