Bolesław I (Vorlage:Lang-cs, Vorlage:Lang-de) (after 1363 - 6 May 1431) was the fourth Duke of Cieszyn. He was the son of Przemysław I Noszak, third Duke of Cieszyn and Elżbieta.

Around 1405-1407 he married Małgorzata, daughter of Jan I, Duke of Racibórz. However, his wife soon passed away, Bolesław I thus married again in 1412. His second wife was Eufemia (called also Ofka), daughter of Siemowit IV of Masovia. Eufemia have birth to five children, four sons and one daughter.

After the death of his father, Bolesław I decided to divide his possessions and on 11 November 1416 finally divided them, keeping in his hands Duchy of Cieszyn, Bytom and half of Głogów.

Just like his father also Bolesław I was active on international stage. In 1414 he participated in the Polish-Teutonic War on the side of Władysław Jagiełło. Bolesław I also supported Bohemian side during the Hussite Wars, but didn't participated in the war itself.

In the internal politics he supported the development of the towns. He ceded several rights to some towns, for example Frýdek and Bielsko. This was also partly motivated by the lack of money in the duchies' budget.

After his death his wife Eufemia with her sons took over the control of the duchy. She continued her husband's policies supporting the towns and in 1438 co-decided in the decision to give Cieszyn rights to mint coins. She also allowed to sell the Duchy of Oświęcim and Duchy of Siewierz to Zbigniew Oleśnicki, bishop of Kraków. She was presumably buried alongside her husband in Dominican church in Cieszyn.

• Idzi Panic: Poczet Piastów i Piastówien cieszyńskich. Urząd Miejski, Cieszyn 2002, ISBN 83-917095-4-X. 

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