Boleslaw Kedzierzawy

Bolesław IV the Curly
19th century portrait by Jan Matejko
High Duke of Poland
Tenure	1146–1173
Predecessor	Władysław II the Exile
Successor	Mieszko III the Old
Duke of Masovia
Tenure	1138–1173
Predecessor	new creation
Successor	Leszek
Duke of Silesia
Tenure	1146–1163
Predecessor	Władysław II the Exile
Successor	Bolesław I the Tall
Duke of Sandomierz
Tenure	1166–1173
Predecessor	Henry
Successor	Casimir II the Just
Born	c. 1125
Died	5 January 1173 [aged 48]
Spouse	Viacheslava of Novgorod Maria
Issue	With Viacheslava: Leszek, Duke of Masovia
House	Piast dynasty
Father	Bolesław III Wrymouth
Mother	Salomea of Berg

Bolesław IV the Curly (Polish: Bolesław Kędzierzawy) (ca. 1125 – 5 January 1173) of the Piast dynasty was Duke of Masovia from 1138 and High Duke of Poland from 1146 until his death.

He was the third son of Duke Bolesław 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, before 1131 and in October 1131, respectively, left him as the eldest son of their parents.

Bolesław was 13 years old at the time of his father's death (1138) and of the legal age to take on the government of the lands he inherited according to his father's testament, the newly created Duchy of Masovia (composed of Masovia and eastern Kuyavia). Because his main domain was Masovia, the prince was called Bolesław of Masovia.

In the first years of his government, young Bolesław remained under the strong influence of his mother Salomea and the Voivode Wszebor, who feared the ambition of his elder half-brother High Duke Władysław II (the first-born son of the late duke by his first wife Zbyslava of Kiev). Władysław II tried to restore the unity of the country and deposed the Junior Dukes.

The disputes with the High-Duke began openly in 1141, when the Dowager Duchess Salomea -without the consent of High Duke Władysław II-, organized a meeting with her sons at her residence in Łęczyca. Here was decided the betrothal of her youngest daughter Agnes with Mstislav II of Kiev, a scion of the Rurik Dynasty — in order to gain allies in a possible conflict — and the division of the Łęczyca lands between Salomea's sons upon her death. However, the Junior Dukes in this first struggle were definitely defeated, because the Kievan Grand Prince Vsevolod II decided to make an alliance with Władysław II, reinforced by the marriage of Vsevolod's daughter Zvenislava with the High Duke's eldest son Bolesław I the Tall. An additional humiliation for Bolesław IV and his brothers was that they were sent by the High Duke on an expedition to the Kievan Rus' as ambassadors during 1142–1143.