| Ismar | |
| Pushpin Map: | Romania |
| Subdivision Type1: | Country |
| Subdivision Name1: | Romania |
| Subdivision Type2: | Counties |
| Subdivision Name2: | Giurgiu County |
| Length: | 27km (17miles) |
| Source1 Coordinates: | 43.9708°N 25.7944°W |
| Source1 Elevation: | 85m (279feet) |
| Mouth: | Câlniștea |
| Mouth Coordinates: | 44.1481°N 25.7783°W |
| Mouth Elevation: | 69m (226feet) |
| Basin Size: | 161km2 |
| Tributaries Left: | Negrile |
The Ismar is a right tributary of the river Câlniștea in Romania. It discharges into the Câlniștea in Naipu. It flows through the villages Radu Vodă, Dimitrie Cantemir, Izvoarele, Chiriacu and Petru Rareș. Its length is 27km (17miles) and its basin size is 161km2.