| Kalkfontein Dam | |
| Name Official: | Kalkfontein Dam |
| Dam Crosses: | Riet River |
| Res Name: | Kalkfontein Dam Reservoir |
| Country: | South Africa |
| Owner: | Department of Water Affairs |
| Dam Length: | 317 m |
| Dam Height: | 36 m |
| Dam Type: | rockfill |
| Purpose: | Irrigation and household |
| Opening: | 1938 (renovated 1977) |
| Res Capacity Total: | 258 274 000 m³ |
| Res Surface: | 3 769.7 ha |
| Coordinates: | -29.4958°N 25.2222°W |
Kalkfontein Dam is a rockfill type dam located on the Riet River, near Koffiefontein, Free State, South Africa. It was established in 1938 and renovated in 1977. The primary purpose of the dam is to serve for irrigation purposes and its hazard potential has been ranked high (3).Kalkfontein Dam reservoir is often quite low (10-20% full) as the upstream area is hot and dry and too small to fill a dam of this size, however during flooding on the Orange River, water is transferred from the Orange River at Vanderkloof Dam to Kalkfontein Dam. In 2021 this led to the reservoir rising from 17.3% to 61.7% in a single week.