| Official Name: | Lonjin |
| Settlement Type: | Village (Selo) |
| Pushpin Map: | Serbia |
| Pushpin Label Position: | bottom |
| Subdivision Type: | Country |
| Subdivision Name: |  Serbia |
| Subdivision Type1: | District |
| Subdivision Type2: | Municipality |
| Subdivision Name2: | Ljubovija |
| Unit Pref: | Imperial |
| Population As Of: | 2002 |
| Timezone: | CET |
| Utc Offset: | +1 |
| Timezone Dst: | CEST |
| Utc Offset Dst: | +2 |
| Coordinates: | 44.2167°N 40°W |
Lonjin is a village in Serbia. It is situated in the Ljubovija municipality, in the Mačva District of Central Serbia. The village had a Serb ethnic majority and a population of 337 in 2002.