Joanna of Austria, Princess of Portugal (b. 1535)
Joanna of Austria (in Castilian, Doña Juana de Austria; in Portuguese, Dona Joana de Áustria, 24 June 1535 – 7 September 1573) was Princess of Portugal by marriage to João Manuel, Prince of Portugal. She served as regent of Spain to her brother Philip II of Spain during his trips to England to marry Mary I from 1554 to 1556, and 1556 to 1559. She was the mother of King Sebastian of Portugal.