| Kato Kastritsi | |
| Name Local: | Κάτω Καστρίτσι |
| Type: | community |
| Coordinates: | 38.2833°N 69°W |
| Elevation: | 96 |
| Periph: | West Greece |
| Periphunit: | Achaea |
| Municipality: | Patras |
| Municunit: | Rio |
| Population As Of: | 2021 |
| Pop Community: | 798 |
| Postal Code: | 265 00 |
| Area Code: | 2160 |
| Licence: | AX |
Kato Kastritsi (Greek, Modern (1453-);: Κάτω Καστρίτσι) is a village and a community in the municipal unit of Rio, Achaea, Greece. The community consists of the villages Kato Kastritsi and Magoula. It is situated at about 100 m elevation in the northwestern foothills of the Panachaiko, 2 km southeast of Rio town centre, and adjacent to the campus of the University of Patras. Ano Kastritsi is 4 km to the southeast.
| Year | Population village | Population community | |
|---|---|---|---|
| 1981 | - | 518 | |
| 1991 | 380 | 677 | |
| 2001 | 514 | 712 | |
| 2011 | 758 | 1,046 | |
| 2021 | 545 | 798 |