Isabella of Austria (1501-1526) was a Spanish princess and the daughter of Philip I of Castile and Joanna of Castile. She became the Queen of Portugal by marrying John III of Portugal in 1525, strengthening the ties between the Spanish and Portuguese crowns. Isabella was known for her intelligence and political acumen. Isabella's marriage was part of a broader strategy to unite the two powerful kingdoms. She had a significant role in the cultural and political life of her time, and her descendants continued to influence European politics. Her life reflects the intricate connections between royal families in 16th-century Europe.