Isabella of Austria, also known as Elizabeth, was born an Archduchess of Austria and Infanta of Castile from the House of Habsburg, and subsequently became Queen of Denmark, Norway and Sweden, under the Kalmar Union, as the wife of King Christian II. She was the daughter of King Philip I and Queen Joanna of Castile and the sister of Charles V, Holy Roman Emperor. She ruled Denmark as regent in 1520.

Charles V was Holy Roman Emperor and Archduke of Austria from 1519 to 1556, King of Spain from 1516 to 1556, and Lord of the Netherlands as titular Duke of Burgundy from 1506 to 1555. He was heir to and then head of the rising House of Habsburg. His dominions in Europe included the Holy Roman Empire, extending from Germany to northern Italy with rule over the Austrian hereditary lands and Burgundian Low Countries, and Spain with its possessions of the southern Italian kingdoms of Naples, Sicily and Sardinia. In the Americas, he oversaw the continuation of Spanish colonization and a short-lived German colonization. The personal union of the European and American territories he ruled was the first collection of realms labelled "the empire on which the sun never sets".