structural:expansion
Inheritances

The Burgundian inheritance included the Habsburg Netherlands, which consisted of a large number of the lordships that formed the Low Countries and covered modern-day Belgium, Netherlands and Luxembourg. It excluded Burgundy proper, annexed by France in 1477, with the exception of Franche-Comté. At the death of Philip in 1506, Charles was recognized Lord of the Netherlands with the title of Charles II of Burgundy. During his childhood and teen years, Charles lived in Mechelen together with his sisters Mary, Eleanor, and Isabella at the court of his aunt Margaret of Austria, Duchess of Savoy. William de Croÿ (later prime minister) and Adrian of Utrecht (later Pope Adrian VI) served as his tutors. The culture and courtly life of the Low Countries played an important part in the development of Charles's beliefs. As a member of the Burgundian Order of the Golden Fleece in his infancy, and later its grandmaster, Charles was educated to the ideals of the medieval knights and the desire for Christian unity to fight the infidel. The Low Countries were very rich during his reign, both economically and culturally. Charles was very attached to his homeland and spent a large part of his life in Brussels and various Flemish cities.

The Spanish inheritance, resulting from a dynastic union of the crowns of Castile and Aragon, included Spain as well as the Castilian possessions in the Americas (the Spanish West Indies and the Province of Tierra Firme) and the Aragonese kingdoms of Naples, Sicily, and Sardinia. Joanna inherited these territories in 1516 while confined, allegedly because she was mentally ill. Charles, therefore, claimed the crowns for himself jure matris, thus becoming co-monarch with Joanna with the title of Charles I of Castile and Aragon or Charles I of Spain. Castile and Aragon together formed the largest of Charles's personal possessions, and they also provided a great number of generals and tercios (the formidable Spanish infantry of the time), while Joanna remained confined in Tordesillas until her death. Plus Ultra, the rendition from French into Latin of Charles's personal motto "Plus Oultre" (Further Beyond), later became the national motto of Spain and features on the country's flag as part of the Spanish coat of arms since the 18th century. However, at his accession to the Iberian thrones, Charles was viewed as a foreign prince.

Two rebellions, the Revolt of the Germanies and the Revolt of the Comuneros, contested Charles's rule in the 1520s. Following these revolts, Charles placed Spanish counselors in a position of power and spent a significant part of his life in Castile, including his final years in a monastery. Indeed, his son and heir, later Philip II of Spain, was born and raised in Castile. Nonetheless, many Spaniards believed that their resources (largely consisting of flows of silver from the Americas) were being used to sustain Imperial-Habsburg policies that were not in the country's interest.

Charles inherited the Austrian hereditary lands in 1519, as Charles I of Austria, and obtained the election as Holy Roman Emperor against the candidacy of the French king. Since the Imperial election, he was known as Emperor Charles V even outside of Germany. The dynastic motto of the House of Habsburg used by Charles was A.E.I.O.U. ("Austria Est Imperare Orbi Universo" — "it is Austria's destiny to rule the world"; although its exact meaning remains disputed). Charles staunchly defended Catholicism as Lutheranism spread. Various German princes broke with him on religious grounds, fighting against him. Charles's presence in Germany was often marked by the organization of imperial diets to maintain religious and political unity.

He was frequently in Northern Italy, often taking part in complicated negotiations with the Popes to address the rise of Protestantism. It is important to note, though, that the German Catholics supported the Emperor. Charles had a close relationship with important German families, like the House of Nassau, many of which were represented at his imperial court. Many German princes, noblemen and generals led his military campaigns against France and the Ottomans or accompanied him in his travels, and the bulk of his army was generally composed of German troops, especially the Imperial Landsknechte.