Maximilian I of Habsburg (22 March 1459 – 12 January 1519), the son of Frederick III, Holy Roman Emperor and Eleanor of Portugal, was King of the Romans (also known as King of the Germans) from 1486 and Holy Roman Emperor from 1493 until his death. He had ruled jointly with his father for the last ten years of his father's reign, from circa 1483. He expanded the influence of the House of Habsburg through both war and marriage, but also lost the Austrian territories in today's Switzerland to the Swiss Confederacy.
By marrying his son Philip to the future Queen Joanna of Castile in 1498, Maximilian established the Habsburg dynasty in Spain and allowed his grandson Charles to hold the throne of both León-Castile and Aragon, therefore causing him to be the first de jure King of Spain. Having outlived his father Philip, Charles succeeded Maximilian as Holy Roman Emperor in 1519, and thus ruled both the Holy Roman Empire and the Spanish Empire simultaneously.