Queen Świętosawa, also known as Saint Sava, was a Polish princess born in the 11th century. She was the daughter of Bolesław I the Brave, the first King of Poland. Świętosawa married Duke Casimir I of Poland, strengthening ties between Poland and the Holy Roman Empire. She is best known for her role in promoting Christianity in Poland and her efforts to support the Catholic Church. After her husband's death, she became a nun and was later canonized as a saint. Her legacy includes her contributions to the spread of Christianity and her influence on Polish history.