Boleslaw IV the Curly (ca.

1125 – 5 January 1173) of the Piast dynasty is Duke of Masovia from 1138 and High Duke of Poland from 1146 until his death.

He is the third son of Duke Boleslaw III Wrymouth of Poland by his second wife Salomea, daughter of the Swabian count Henry of Berg.

The death of his older brothers, Leszek and Casimir, in August and October 1131, respectively, leave him as the eldest son of their parents.