| Official Name: | Mazaj |
| Native Name: | مزج |
| Settlement Type: | village |
| Pushpin Map: | Iran |
| Mapsize: | 150px |
| Subdivision Type: | Country |
| Subdivision Type1: | Province |
| Subdivision Name1: | Semnan |
| Subdivision Type2: | County |
| Subdivision Name2: | Shahrud |
| Subdivision Type3: | Bakhsh |
| Subdivision Name3: | Bastam |
| Subdivision Type4: | Rural District |
| Subdivision Name4: | Kalat-e Hay-ye Gharbi |
| Population As Of: | 2006 |
| Population Total: | 666 |
| Population Density Km2: | auto |
| Timezone: | IRST |
| Utc Offset: | +3:30 |
| Timezone Dst: | IRDT |
| Utc Offset Dst: | +4:30 |
| Coordinates: | 36.6103°N 55.4033°W |
Mazaj (Persian: مزج, also Romanized as Mazj; also known as Magās, Maghāzu, and Maghz) is a village in Kalat-e Hay-ye Gharbi Rural District, Bastam District, Shahrud County, Semnan Province, Iran. At the 2006 census, its population was 666, in 215 families.