Charles was the heir of three of Europe's leading dynasties: the Houses of Valois-Burgundy (through his paternal grandmother), Habsburg, and Trastámara (his maternal grandparents were the Catholic Monarchs of Spain). Upon the death of his maternal grandmother Queen Isabella I of Castile in 1504, Charles's mother Joanna inherited the kingdom of Castile. She was mentally insane and held little real power, with her father, King Ferdinand II of Aragon, and (briefly) her husband and co-ruler, Philip, Charles's father, serving as regents. Upon the death of Ferdinand V in 1516, Charles and Joanna ruled both Castile and Aragon together, as a unified Spain, although Joanna remained in confinement. Charles inherited the Netherlands and the Free County of Burgundy as heir of the House of Valois-Burgundy. As a Habsburg, he inherited Austria and other lands in central Europe. He was also elected to succeed his grandfather, Maximilian I, as Holy Roman Emperor, a title held by the Habsburgs since 1440. From the Spanish House of Trastámara, he inherited the Crown of Castile, which was developing a nascent empire in the Americas and Asia, and the Crown of Aragon, which included a Mediterranean empire extending to Southern Italy. Charles was the first king to rule Castile and Aragon simultaneously in his own right, and as a result he is often referred to as the first king of Spain. The personal union under Charles of the Holy Roman Empire with the Spanish Empire was the closest Europe would come to a universal monarchy since the death of Louis the Pious (778–840).
In 1506, Charles inherited his father's Burgundian territories, most notably the Low Countries and Franche-Comté. Most of the holdings were fiefs of the German Kingdom (part of the Holy Roman Empire), except his birthplace of Flanders, which was still a French fief, a last remnant of what had been a powerful player in the Hundred Years' War. As he was a minor, his aunt Margaret of Austria (born as Archduchess of Austria and in both her marriages as the Dowager Princess of Asturias and Dowager Duchess of Savoy) acted as regent, as appointed by Emperor Maximilian until 1515. She soon found herself at war with France over the question of Charles' requirement to pay homage to the French king for Flanders, as his father had done. The outcome was that France relinquished its ancient claim on Flanders in 1528.
Thus, after the celebration of Ferdinand II's obsequies on 14 March 1516, Charles was proclaimed king of the crowns of Castile and Aragon jointly with his mother. Finally, when the Castilian regent Cardinal Jiménez de Cisneros accepted the fait accompli, he acceded to Charles's Desire to be proclaimed king and imposed his enstatement throughout the kingdom. Charles arrived in his new kingdoms in autumn of 1517. Jiménez de Cisneros came to meet him but fell ill along the way, not without a suspicion of poison, and he died before meeting the King.
Negotiations for Charles's marriage first began shortly after his arrival in Spain, with the Spanish nobles expressing their wishes for him to marry his first cousin the Infanta Isabella of Portugal, daughter of King Manuel I of Portugal and Charles's aunt Queen Maria of Aragon, and sister of King John III of Portugal. The nobles desired for Charles to marry a Princess of Spanish blood and a marriage to Isabella would secure an alliance between Spain and Portugal. The 18 year old King, however, was in no hurry to marry and ignored the nobles' advice. Instead of marrying Isabella, he sent his sister Eleanor of Austria to marry Isabella's widowed father King Manuel in 1518. In 1521, on the advice of his Flemish advisors, especially william de Croÿ, Charles became engaged to his other first cousin Princess Mary Tudor, daughter of his aunt Catherine of Aragon and King Henry VIII of England in order to secure an alliance with England. However, this engagement was very problematic; Mary Tudor was only 6 years old at the time, sixteen years Charles's junior, which meant that he would have to wait for her to be old enough to marry.
After the death of his paternal grandfather, Maximilian, in 1519, Charles inherited the Habsburg Monarchy. He was also the natural candidate of the electors to succeed his grandfather as Holy Roman Emperor. He defeated the candidacies of Frederick III, Elector of Saxony, Francis I of France, and Henry VIII of England. The electors gave Charles the crown on 28 June 1519. On 26 October 1520 he was crowned in Germany and some ten years later, on 22 February 1530, he was crowned Holy Roman Emperor by Pope Clement VII in Bologna, the last Emperor to receive a papal coronation.
Coat of arms of Charles I of Spain and V of Germany according to the description: Arms of Charles I added to those of Castile, Leon, Aragon, Two Sicilies and Granada present in the previous coat, those of Austria, ancient Burgundy, modern Burgundy, Brabant, Flanders and Tyrol. Charles I also incorporates the pillars of Hercules with the inscription "Plus Ultra", representing the overseas empire and surrounding coat with the collar of the Golden Fleece, as sovereign of the Order ringing the shield with the imperial crown and Acola double-headed eagle of the Holy Roman Empire and behind it the Spanish Cross of Burgundy. From 1520 added to the corresponding quarter to Aragon and Sicily, one in which the arms of Jerusalem, Naples and Navarre are incorporated.
As Holy Roman Emperor, Charles called Martin Luther to the Diet of Worms in 1521, promising him safe conduct if he would appear. Initially dismissing Luther's theses as "an argument between monks", he later outlawed Luther and his followers in that same year but was tied up with other concerns and unable to take action against Protestantism. The Peasants' Revolt in Germany broke out from 1524 to 1526, and in 1531 the Lutheran Schmalkaldic League was formed. Charles delegated increasing responsibility for Germany to his brother Ferdinand while he concentrated on problems elsewhere.
Despite holding the imperial throne, Charles's real authority was limited by the German princes. They gained a strong foothold in the Empire's territories, and Charles was determined not to let this happen in the Netherlands. An inquisition was established as early as 1522. In 1550, the death penalty was introduced for all cases of unrepentant heresy. Political dissent was also firmly controlled, most notably in his place of birth, where Charles, assisted by the Duke of Alba, personally suppressed the Revolt of Ghent in mid-February 1540.
Soon resistance to the Emperor arose because of heavy taxation to support foreign wars in which Castilians had little interest, and because Charles tended to select Flemings for high offices in Spain and America, ignoring Castilian candidates. The resistance culminated in the Revolt of the Comuneros, which Charles suppressed. Immediately after crushing the Castilian revolt, Charles was confronted again with the hot issue of Navarre when King Henry II attempted to reconquer the kingdom. Main military operations lasted until 1524, when Hondarribia surrendered to Charles's forces, but frequent cross-border clashes in the western Pyrenees only stopped in 1528 (Treaties of Madrid and Cambrai).
By 1525, Charles was no longer interested in an alliance with England and could not wait any longer to have legitimate children and heirs. Following his victory in the Battle of Pavia, Charles abandoned the idea of an English alliance, cancelled his engagement to Mary Tudor and decided to marry Isabella and form an alliance with Portugal. He wrote to his cousin King John, making a double marriage contract - Charles would marry Isabella and John would marry Charles's youngest sister Catherine of Austria. A marriage to Isabella was more beneficiary for Charles, as she was closer to him in age, was fluent in Spanish and provided him with a very handsome dowry of 900,000 Portuguese cruzados or Castilian folds that would help to solve his financial problems brought on by the Italian Wars.
On 10 March 1526, Charles and Isabella met at the Alcázar Palace in Seville. The marriage was originally a political arrangement, but on their first meeting, the couple fell deeply in love, with Isabella captivating the Emperor with her beauty and charm. They were married that very same night in a quiet ceremony in the Hall of Ambassadors. Following their wedding, Charles and Isabella spent a long and happy honeymoon at the Alhambra in Granada. Wishing to establish their residence in the Alhambra palaces, Charles began the construction of the Palace of Charles V in 1527, which was intended as a permanent residence befitting an Emperor and Empress. However, the palace was not completed during their lifetime and remained roofless until the late 20th century.
When he was released, however, Francis had the Parliament of Paris denounce the treaty because it had been signed under duress. France then joined the League of Cognac that Pope Clement VII had formed with Henry VIII of England, the Venetians, the Florentines, and the Milanese to resist imperial domination of Italy. In the ensuing war, Charles's sack of Rome (1527) and virtual imprisonment of Pope Clement VII in 1527 prevented the Pope from annulling the marriage of Henry VIII of England and Charles's aunt Catherine of Aragon, so Henry eventually broke with Rome, thus leading to the English Reformation. In other respects, the war was inconclusive. In the Treaty of Cambrai (1529), called the "Ladies' Peace" because it was negotiated between Charles's aunt and Francis' mother, Francis renounced his claims in Italy but retained control of Burgundy.
In 1528 Charles assigned a concession in Venezuela Province to Bartholomeus V. Welser, in compensation for his inability to repay debts owed. The concession, known as Klein-Venedig (little Venice), was revoked in 1546. In 1550, Charles convened a conference at Valladolid in order to consider the morality of the force used against the indigenous populations of the New World, which included figures such as Bartolomé de las Casas.
Suleiman won the contest for mastery of the Mediterranean, in spite of Spanish victories such as the conquest of Tunis in 1535. The regular Ottoman fleet came to dominate the Eastern Mediterranean after its victories at Preveza in 1538 and Djerba in 1560 (shortly after Charles's death), which severely decimated the Spanish marine arm. At the same time, the Muslim Barbary corsairs, acting under the general authority and supervision of the Sultan, regularly devastated the Spanish and Italian coasts, crippling Spanish trade and chipping at the foundations of Habsburg power.
In 1536 Francis I of France allied himself with Suleiman against Charles. While Francis was persuaded to sign a peace treaty in 1538, he again allied himself with the Ottomans in 1542 in a Franco-Ottoman alliance. In 1543 Charles allied himself with Henry VIII and forced Francis to sign the Truce of Crépy-en-Laonnois. Later, in 1547, Charles signed a humiliating treaty with the Ottomans to gain himself some respite from the huge expenses of their war.
In addition, Habsburg trade in the Mediterranean was consistently disrupted by the Ottoman Empire. In 1538 a Holy League consisting of all the Italian states and Spain was formed to drive the Ottomans back, but it was defeated at the Battle of Preveza. Decisive naval victory eluded Charles; it would not be achieved until after Charles's death, at the Battle of Lepanto in 1571.
The marriage lasted for thirteen years until Isabella died at the age of 35 on 1 May 1539. The Empress contracted a fever during the third month of her seventh pregnancy, which resulted in antenatal complications that caused her to miscarry and give birth to a stillborn son. She died two weeks later. Charles was left so grief-stricken by his wife's death that he shut himself up in a monastery for two months where he prayed and mourned for her in solitude. In the aftermath, Charles never recovered from Isabella's death; he dressed in black for the rest of his life, and, unlike most kings of the time, he never remarried. In memory of his wife, the Emperor commissioned the Painter Titian to paint several posthumous portraits of Isabella; the portraits that were produced included Titian's Portrait of Empress Isabel of Portugal and La Gloria. Charles kept these portraits with him whenever he travelled and they were among those that he later brought with him to the Monastery of Yuste in 1557 after his retirement.
Charles also paid tribute to Isabella's memory with music, when in 1540, he commissioned the Flemish Composer Thomas Crecquillon to compose new music as a memorial to her. Crecquillon composed his Missa 'Mort m'a privé' in memory of the Empress, which itself expresses the Emperor's grief and great wish for a heavenly reunion with his beloved wife.
In 1545, the opening of the Council of Trent began the Counter-Reformation, and Charles won to the Catholic cause some of the princes of the Holy Roman Empire. In 1546 (the year of Luther's death), he outlawed the Schmalkaldic League (which had occupied the territory of another prince). The next year his forces drove the League's troops out of southern Germany, and defeated John Frederick, Elector of Saxony and Philip of Hesse at the Battle of Mühlberg, capturing both. At the Augsburg Interim in 1548, he created a solution giving certain allowances to Protestants until the Council of Trent would restore unity. However, members of both sides resented the Interim and some actively opposed it. In 1552 Protestant princes, in alliance with Henry II of France, rebelled again, which caused Charles to retreat to the Netherlands.
Charles extended the Burgundian territory with the annexation of Tournai, Artois, Utrecht, Groningen and Guelders. The Seventeen Provinces had been unified by Charles's Burgundian ancestors, but nominally were fiefs of either France or the Holy Roman Empire. In 1549, Charles issued a Pragmatic Sanction, declaring the Low Countries to be a unified entity of which his family would be the heirs.
A final war erupted with Francis' son and successor, Henry II, in 1551. Henry won early success in Lorraine, where he captured Metz, but French offensives in Italy failed. Charles abdicated midway through this conflict, leaving further conduct of the war to his son, Philip II, and his brother, Ferdinand I, Holy Roman Emperor.
Charles retired to the Monastery of Yuste in Extremadura but continued to correspond widely and kept an interest in the situation of the empire. He suffered from severe gout. Some scholars think Charles decided to abdicate after a gout attack in 1552 forced him to postpone an attempt to recapture the city of Metz, where he was later defeated. He lived alone in a secluded monastery, with clocks Li Ning every wall, which some historians believe were symbols of his reign and his lack of time. In an act designed to "merit the favour of heaven", about six months before his death Charles staged his own funeral, complete with shroud and coffin, after which he "rose out of the coffin, and withdrew to his apartment, full of those awful sentiments, which such a singular solemnity was calculated to inspire."
Charles was accepted as sovereign, even though the Spanish felt uneasy with the Imperial style. Spanish kingdoms varied in their traditions. Castile was an authoritarian kingdom, where the monarch's own will easily overrode law and the Cortes. By contrast, in the kingdoms of the crown of Aragon, and especially in the Pyrenean kingdom of Navarre, law prevailed, and the monarchy was a contract with the people. This became an inconvenience and a matter of dispute for Charles V and later kings, since realm-specific traditions limited their absolute power. With Charles, government became more absolute, even though until his mother's death in 1555 Charles did not hold the full kingship of the country.
Charles abdicated the parts of his empire piecemeal. First he abdicated the thrones of Sicily and Naples, both fiefs of the Papacy, and the Duchy of Milan to his son Philip in 1554. Upon Charles's abdication of Naples on 25 July, Philip was invested with the kingdom (officially "Naples and Sicily") on 2 October by Pope Julius III. The abdication of the throne of Sicily, sometimes dated to 16 January 1556, must have taken place before Joanna's death in 1555. There is a record of Philip being invested with this kingdom (officially "Sicily and Jerusalem") on 18 November 1554 by Julius. These resignations are confirmed in Charles's will from the same year. The most famous—and public—abdication of Charles took place a year later, on 25 October 1555, when he announced to the States General of the Netherlands his abdication of those territories and the county of Charolais and his intention to retire to a monastery. He abdicated as ruler of the Spanish Empire in January 1556, with no fanfare, and gave these possessions to Philip. In September 1556, he abdicated as Holy Roman Emperor in favor of his brother Ferdinand, although the abdication was not formally accepted by the Electors of the Empire until 1558. The delay had been at the request of Ferdinand, who had been concerned about holding a risky election in 1556.
In August 1558, Charles was taken seriously ill with what was later revealed to be malaria. He died in the early hours of the morning on 21 September 1558, at the age of 58, holding in his hand the cross that his wife Isabella had been holding when she died.
Charles was originally buried in the chapel of the Monastery of Yuste, but he left a codicil in his last will and testament asking for the establishment of a new religious foundation in which he would be reburied with Isabella. Following his return to Spain in 1559, their son Philip undertook the task of fulfilling his father's wish when he founded the Monastery of San Lorenzo de El Escorial. After the Monastery's Royal Crypt was completed in 1574, the bodies of Charles and Isabella were relocated and re-interred into a small vault directly underneath the altar of the famous Basilica of the Monastery, in accordance with Charles's wishes to be buried "half-body under the altar and half-body under the priest's feet" side by side with Isabella. They remained in this vault until 1654 when they were later moved into the Royal Pantheon of Kings by their great-grandson Philip IV, who, in doing so, disrespected his great-grandfather's wishes.
After these events, Navarre remained a matter of domestic and international litigation still for a century (a French dynastic claim to the throne did not end until the French Revolution in 1789). Charles wanted his son and heir Philip II to marry the heiress of Navarre, Jeanne d'Albret. Jeanne was instead forced to marry william, Duke of Julich-Cleves-Berg, but that childless marriage was annulled after four years. She next married Antoine de Bourbon, and both she and their son would oppose Philip II in the French Wars of Religion.