| Lake Onslow | |
|---|---|
| Location | Otago, South Island |
| Lake type | reservoir |
| Primary inflows | Teviot River |
| Primary outflows | Teviot River |
| Basin countries | New Zealand |
| Surface elevation | 700 m |
Lake Onslow is a man-made lake east of Roxburgh and south of Alexandra in the Otago region of New Zealand. It lies 700 m (2,300 ft) above sea level. It was formed in 1890 by the damming of the Teviot River and Dismal Swamp.
The lake is the subject of several paintings by the late Edward Mullor.