| Allaikha | |
| Source1 Location: | Polousny Range |
| Mouth: | Indigirka |
| Mouth Coordinates: | 70.5286°N 147.7139°W |
| Subdivision Type1: | Country |
| Subdivision Name1: | Russia |
| Length: | 563km (350miles) |
| Basin Size: | 12400km2 |
| Pushpin Map: | Russia Sakha Republic |
| Pushpin Map Caption: | Location in Sakha, Russia |
The Allaikha (Russian: Алла́иха; Yakut: Аллайыаха, Allayıaxa)[1] is a river of Sakha Republic, Russia, a left hand tributary of the Indigirka. It is long, and has a drainage basin of .
The Allaikha has its source in the northern slopes of the Polousny Range at the Swan Lake, in the confluence of two small rivers, Fena (Фена) and Elikcheen (Эликчээн). It flows meandering roughly northeastwards across the Yana-Indigirka Lowland.[2] It finally joins the Indigirka about 15km (09miles) north of Chokurdakh.[3]
There are more than four thousand lakes in the basin of the Allaikha. Its most important tributary is the Ot-Yuryakh from the left.[4]