| Kachi Mayu | |
| Name Etymology: | Quechua |
| Subdivision Type1: | Country |
| Subdivision Name1: | Bolivia |
| Subdivision Type3: | Region |
| Subdivision Name3: | Chuquisaca Department |
| Mouth Location: | Chuquisaca Department (Yotalla Municipality) / Potosí Department |
| Mouth Coordinates: | -19.3133°N -65.2664°W |
Kachi Mayu (Quechua kachi salt, mayu river, "salt river", also spelled Cachi) is a Bolivian river in the Chuquisaca Department, Oropeza Province, in the Sucre and Yotalla Municipalities. It is a left tributary of the Pillku Mayu, not to be confused with the Kachi Mayu in the Oruro Department which is the headwater of the Pillku Mayu. The confluence is on the border of the Yotalla Municipality and the Potosí Department, west of the village of Tasapampa.