| Official Name: | Hesar-e Pain |
| Native Name: | حصارپائين |
| Settlement Type: | village |
| Pushpin Map: | Iran |
| Mapsize: | 150px |
| Subdivision Type: | Country |
| Subdivision Type1: | Province |
| Subdivision Name1: | Tehran |
| Subdivision Type2: | County |
| Subdivision Name2: | Damavand |
| Subdivision Type3: | Bakhsh |
| Subdivision Name3: | Central |
| Subdivision Type4: | Rural District |
| Subdivision Name4: | Tarrud |
| Population As Of: | 2006 |
| Population Total: | 421 |
| Population Density Km2: | auto |
| Timezone: | IRST |
| Utc Offset: | +3:30 |
| Timezone Dst: | IRDT |
| Utc Offset Dst: | +4:30 |
| Coordinates: | 35.6672°N 52.03°W |
| Elevation M: | 1820 |
Hesar-e Pain (Persian: حصارپائين, also Romanized as Ḩeşār-e Pā’īn, Ḩeşar Pā’īn, and Hisār Pāīn; also known as Ḩeşār-e Pā’īn va Qūrdlū) is a village in Tarrud Rural District, in the Central District of Damavand County, Tehran Province, Iran. At the 2006 census, its population was 421, in 109 families.