| Ruja | |
| Pushpin Map: | Romania |
| Subdivision Type1: | Country |
| Subdivision Name1: | Romania |
| Subdivision Type2: | Counties |
| Subdivision Name2: | Iași County |
| Subdivision Type3: | Villages |
| Subdivision Name3: | Valea Seacă, Lunca |
| Length: | 12km (07miles) |
| Mouth: | Siret |
| Mouth Location: | Lunca |
| Mouth Coordinates: | 47.275°N 26.7574°W |
| Basin Size: | 66km2 |
| Tributaries Right: | Irmolea, Gâștești |
| Custom Label: | River code |
| Custom Data: | XII.1.26a |
The Ruja is a right tributary of the river Siret in Romania. It flows into the Siret north of Pașcani. Its length is 12km (07miles) and its basin size 66km2.