Philip I of Portugal, also known as Philip II of Spain, ruled as King of Portugal from 1598 to 1621. He was born on May 21, 1578, and was the son of Philip II of Spain and Anna of Austria. His reign marked the period of the Iberian Union, where Portugal and Spain were united under a single monarch. During his rule, Philip faced challenges such as resistance from Portuguese nobility and conflicts in Asia and Africa. His reign is often noted for the decline of Portuguese maritime power and the loss of independence, which lasted until 1640 when Portugal restored its sovereignty.