page_title: Siemowit I of Masovia
hierarchical_section_title: Siemowit I of Masovia
context_page_description: Siemowit I of Masovia, was a Polish prince member of the House of Piast, Duke of Czersk during 1247-1248, Duke of Masovia during 1248-1262, ruler over Sieradz during 1259-1260.
  He was the sixth son of Konrad I of Masovia and his wife Agafia of Rus.
context_section_description: Siemowit I of Masovia (Polish: Siemowit (Ziemowit) I mazowiecki) (d. 23 June 1262), was a Polish prince member of the House of Piast, Duke of Czersk during 1247-1248, Duke of Masovia (except Dobrzyń) during 1248-1262, ruler over Sieradz  during 1259-1260.
  He was the sixth son of Konrad I of Masovia and his wife Agafia of Rus.
caption: Siemowit I, Duke of Masovia by Jan Matejko
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