Miecław's Rebellion (Polish: bunt Miecława) was a military conflict fought from c. 1037 to 1047 between the Duchy of Poland under Casimir I the Restorer and its ally, Kievan Rus', led by Yaroslav the Wise, against the forces of Miecław, the self-proclaimed leader of a breakaway state, who was allied with the Duchy of Pomerelia and the Yotvingians.

[2] Seizing the opportunity, around 1038, Miecław, the king's cup-bearer, declared the independence of his own state in Masovia from the rest of Poland, and started his own royal dynasty.

[1] He had formed an alliance with Yaroslav the Wise, Grand Prince of Kiev and the leader of Kievan Rus', by marrying Maria Dobroniega.

The battle ended with a decisive Polish victory and the destruction of Miecław's army and led to the signing of a truce between both sides.

[5][6] The location of this battle remains unknown in modern times, though it was known to the 11th-century historian Gallus Anonymus, according to whom it took place near the river with the bluff edge.