Casimir I of Opole

Casimir I
Duke of Opole-Racibórz
Seal of Casimir I, 1226
Spouse(s)	Viola, Duchess of Opole
Noble family	Silesian Piasts
Father	Mieszko I Tanglefoot
Mother	Ludmilla
Born	c.  1179/80
Died	13 May 1230(1230-05-13)
Buried	Czarnowąsy monastery

Casimir I of Opole (Polish: Kazimierz I opolski; c.  1178/79 – 13 May 1230), a member of the Piast dynasty, was a Silesian duke of Opole and Racibórz from 1211 until his death.

Casimir was the eldest child and only son of Duke Mieszko I Tanglefoot and his wife Ludmilla, probably a Bohemian princess of the Přemyslid dynasty. In 1172/73 his father had divided the Silesian lands with his elder brother Bolesław I the Tall and his nephew Duke Jarosław of Opole, and went on to rule as Duke of Racibórz in Upper Silesia.

Little is known about the early years of Casimir's life, except for his own birth, which was the pretext for an agreement between his father and Casimir II the Just, who since 1177 ruled as High Duke of Poland having deposed his elder brother Mieszko III the Old. Casimir II aimed to break the long-time alliance of Mieszko I Tanglefoot with his uncle Mieszko III the Old and in return granted to the Racibórz duke the Lesser Polish districts of Bytom, Oświęcim and Pszczyna as a gift. After the birth of Mieszko Tanglefoot's son and heir, Casimir II the Just stood as the child's godfather who was also named after him.

Mieszko I Tanglefoot significantly enlarged his territory, when after the death of his elder brother Bolesław I in 1201 he conquered the Duchy of Opole. Bolesław's son and heir, Duke Henry the Bearded had to cede the Opole lands to his uncle and also renounced any inheritance claims to Mieszko's Upper Silesian duchies. Upon the death of his uncle Miesko III the Old in 1202, Mieszko also raised claims to the Kraków throne, though he could not succeed until 1210.