| Dienvidsusēja | |
| Map: | Fluss-lv-Dienvidsusēja.png |
| Mouth: | Nemunėlis (Mēmele) |
| Mouth Coordinates: | 56.403°N 24.9241°W |
| Subdivision Type1: | Country |
| Length: | 114km (71miles) |
| Source1 Elevation: | 81m (266feet) |
| Discharge1 Avg: | 246L/s |
| Basin Size: | 1220.9km2 (1192.5km2 within Latvia) |
| Tributaries Right: | Zalvīte |
The Dienvidsusēja (also known as Susēja or Suseja; Lithuanian: Susėja) is a river of Latvia and a right tributary of the river Mēmele. It flows for 114 kilometres. For 4.2 km, the river forms the border between Latvia and Lithuania. The river flows through Aknīste town, Nereta village and several smaller settlements.