Catherine of Austria (1507-1578) was a member of the Habsburg dynasty and the daughter of Philip I of Castile and Joanna of Castile. She became the Queen of Portugal through her marriage to John III of Portugal in 1525, strengthening ties between the Habsburgs and the Portuguese crown. Catherine was known for her piety and dedication to her family. She had several children, including Sebastian of Portugal, who would later become king. Her life was marked by the political and religious challenges of the time, particularly the Protestant Reformation and its impact on European politics.