Charles V (24 February, 1500–21 September 1558) was King of Aragon from 1516 to 1554, king of Castile from 1516 to 1556, and Holy Roman Emperor from 1519 to 1556. In Aragon and Castile, he ruled officially as Charles I, though he is referred to by the ordinal he used as Holy Roman Emperor more often. He was the son of Philip and Joanna of Castile. His maternal grandparents were Ferdinand II of Aragon and Isabella I of Castile. His paternal grandparents were Maximilian I, Holy Roman Emperor and Marie, Duchess of Burgundy.