| Andi Koysu | |
| Pushpin Map: | Russia Dagestan#Georgia |
| Source1 Coordinates: | 42.3547°N 45.6585°W |
| Mouth Coordinates: | 42.7906°N 46.7963°W |
| Subdivision Type1: | Countries |
| Length: | 144km (89miles) |
| Basin Size: | 4810km2 |
The Andi Koysu (Russian: Андийское Койсу - Andiyskoye Koysu, Georgian: ანდის ყოისუ - Andis Qoisu) is a river in Dagestan (Russia) and Georgia. It starts at the confluence of the rivers Pirikiti Alazani and Tushetis Alazani, near Omalo in the Tusheti region of Georgia. It is 144km (89miles) long or 192km (119miles) including its longest source river, Tushetis Alazani, and its drainage basin covers 4810km2.[1] At its confluence with the Avar Koysu, near the village Gimry in central Dagestan, it forms the river Sulak.