Władysław I of Płock

Władysław I of Płock (pl: Władysław I płocki; 1406/09 - 11/12 December 1455), was a Polish prince member of the House of Piast from the Masovian branch. He was a Duke of Płock, Rawa Mazowiecka, Gostynin, Sochaczew, Belz, Płońsk, Zawkrze and Wizna during 1426-1434 jointly with his brothers, after the division of the paternal inheritance between him and his brothers in 1434, sole ruler over Płock, Płońsk, Wizna and Zawkrze; in 1442 he reunited all their patrimony (except Gostynin).

He was the fifth son of Siemowit IV, Duke of Masovia and Alexandra of Lithuania, daughter of Algirdas.

His first appearance took place in March 1424, when along with his brothers Siemowit V, Casimir II and Trojden II, Władysław I attended the wedding and coronation of King Władysław II Jagiełło's third wife, Sophia of Halshany.

Two years later, on 21 January 1426, after the death of their father, Władysław I and his brothers inherited his lands; not wanting to further weakened their positions and domains with subsequents divisions, they decided to co-rule all their paternal inheritance. Eight months later, on 8 September, Władysław I and his brothers Siemowit V and Trojden II paid homage to the Polish King at Sandomierz.

In 1431 as Polish vassals, Władysław I and his brothers take part in the campaign in Volhynia against Švitrigaila, although he didn't play a greater part on it.

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