| Łydynia | |
| Mouth Location: | Wkra |
| Mouth Coordinates: | 52.7066°N 20.4448°W |
| Subdivision Type1: | Country |
| Length: | 72km (45miles) |
Łydynia is a river of north-eastern central Poland, a left tributary of the Wkra at the town of Sochocin, with an overall length of 72 kilometers.[1]
The river flows past Ciechanów and its ancient Mazovian ducal castle. Its own tributaries include the Giedniówka, the Dunajczyk, the Stawnica, and the Pławnica.