| En Name: | Achi-Su |
| Ru Name: | Ачи-Су |
| Loc Name1: | Ачису |
| Loc Lang1: | Dargwa |
| Coordinates: | 42.65°N 88°W |
| Map Label Position: | right |
| Federal Subject: | Republic of Dagestan |
| Adm District Jur: | Karabudakhkentsky District |
| Adm Selsoviet Jur: | Achi-Su Settlement |
| Adm Selsoviet Type: | Settlement |
| Adm Ctr Of: | Achi-Su Settlement |
| Inhabloc Cat: | Urban-type settlement |
| Mun District Jur: | Karabudakhkentsky Municipal District |
| Urban Settlement Jur: | Achi-Su Urban Settlement |
| Mun Admctr Of: | Achi-Su Urban Settlement |
| Pop 2010Census: | 1679 |
| Postal Codes: | 368538 |
| Achi-Su population | |
| Label1: | 2010 Census |
| Data1: | 1,679 |
| Label2: | 2002 Census |
| Data2: | 1,622 |
| Label3: | 1989 Census |
| Data3: | 1,161 |
| Label4: | 1979 Census |
| Data4: | 1,037 |
Achi-Su (Russian: Ачи-Су), also known as Achisu (Russian: Ачису),[1] is an urban locality (an urban-type settlement) in Karabudakhkentsky District of the Republic of Dagestan, Russia. As of the 2010 Census, its population was 1,679.
Within the framework of administrative divisions, the urban-type settlement of Achi-Su is incorporated within Karabudakhkentsky District as Achi-Su Settlement (an administrative division of the district).[2] As a municipal division, Achi-Su Settlement is incorporated within Karabudakhkentsky Municipal District as Achi-Su Urban Settlement.[3]