| Lunain | |
| Map: | Lunain.png |
| Source1 Coordinates: | 48.1106°N 3.1458°W |
| Mouth Coordinates: | 48.3358°N 2.7822°W |
| Subdivision Type1: | Country |
| Length: | 51.4km (31.9miles) |
| Source1 Elevation: | 185m (607feet) |
| Mouth Elevation: | 50m (160feet) |
The Lunain (in French pronounced as /lynɛ̃/) is a 51.4km (31.9miles) long river in the Yonne and Seine-et-Marne departments in north-central France. It is a right tributary of the Loing. Its source is in Yonne, less than 3km (02miles) south-west of Égriselles-le-Bocage. It joins the Loing at Épisy in Seine-et-Marne.