A regent is “a person appointed to administer a state because the monarch is a minor, is absent or is incapacitated.”
Catherine of Austria was born on 14 January 1507 as the daughter of Joanna of Castile and Philip I of Castile, who had sadly passed away in September 1506. Joanna was forced into confinement by her father, and Catherine was the only one of her children to be with her in her confinement. When the time came for her to marry, she was at last released.
On 10 February 1525, Catherine married King John III of Portugal, who was also her first cousin. They would go on to have nine children, but only two survived to adulthood. When her husband died in 1557, all their children were dead, and he was succeeded by their grandson, Sebastian. She was challenged for the regency of the three-year-old King by her daughter-in-law, Joanna. With mediation by her brother Charles V, Holy Roman Emperor it was decided that Catherine should act as regent as Joanna was needed in Spain in the absence of Philip II, her brother.
She served as regent of Portugal from 1557 until 1562 when she turned over the regency to Henry of Portugal, a son of King Manuel I of Portugal. After this, she retired to a convent but kept supervising Sebastian’s upbringing. She died on 12 February 1578 and did not live to see Sebastian’s death in battle just six months later.