| Official Name: | Gerd Ab |
| Native Name: | گرداب |
| Settlement Type: | village |
| Pushpin Map: | Iran |
| Mapsize: | 150px |
| Subdivision Type: | Country |
| Subdivision Type1: | Province |
| Subdivision Name1: | Mazandaran |
| Subdivision Type2: | County |
| Subdivision Name2: | Abbasabad |
| Subdivision Type3: | Bakhsh |
| Subdivision Name3: | Salman Shahr |
| Subdivision Type4: | Rural District |
| Subdivision Name4: | Langarud |
| Population As Of: | 2006 |
| Population Total: | 328 |
| Population Density Km2: | auto |
| Timezone: | IRST |
| Utc Offset: | +3:30 |
| Timezone Dst: | IRDT |
| Utc Offset Dst: | +4:30 |
| Coordinates: | 36.6761°N 51.1133°W |
Gerd Ab (Persian: گرداب, also Romanized as Gerd Āb; also known as Gerdāb Langā and Langā) is a village in Langarud Rural District, Salman Shahr District, Abbasabad County, Mazandaran Province, Iran. At the 2006 census, its population was 328, in 83 families.