Isabella of Austria (Isabel; 18 July 1501 – 19 January 1526), 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.
Her upbringing, overseen by her aunt Archduchess Margaret, was marked by a comprehensive education in Mechelen under the guidance of notable humanists like Juan Luis Vives and Adrian of Utrecht. In 1514, she entered into a strategic marriage with Christian II of Denmark, Norway, and Sweden. However, the marriage encountered early challenges with diplomatic tensions arising from Christian II's existing relationship with Dyveke Sigbritsdatter, his Dutch mistress. Following Dyveke's death in 1517, the relations between Isabella and her husband significantly improved, and Isabella was entrusted with the position of regent in 1520 and political advisor to the king.
In 1523, her husband, King Christian II, was deposed. The political upheaval prompted the Danish royal family, including Isabella and her children, to seek refuge in various European states, such as England, Saxony and the Habsburg Netherlands. During this exile, Isabella strongly advocated for her husband's cause. In 1524, she participated in the Imperial Diet in Nürnberg, where she campaigned on behalf of King Christian II, seeking support for his restoration to the Danish throne.
Her travels through Germany, England, and the Netherlands contributed to her evolving religious sympathies for the Protestant movement. Isabella's death in 1526 prompted widespread mourning. She received both Protestant and Catholic communion, but the Habsburgs declared that she had died a fervent Catholic.
Isabella was born on 18 July 1501 in Brussels as the third child of Philip the Handsome, ruler of the Habsburg Netherlands and Joanna the Mad, heiress to the Spanish kingdoms of Castile and Aragon. Her father was the son of the reigning Holy Roman Emperor Maximilian I and his deceased consort Mary, Duchess of Burgundy, while her mother was the daughter of the Catholic Monarchs Ferdinand II of Aragon and Isabella I of Castile, after whom she is named. She was baptized in Brussels by the Bishop of Cambrai, Henri de Berghes.
She had two older siblings, Eleanor and Charles, as well as three younger siblings Ferdinand, Mary and Catherine. Isabella and her siblings were considered the "noblest children" of her time. Her brothers became the most powerful men in Europe as Holy Roman Emperors. Her sisters became queens in Portugal and France, Bohemia and Hungary, respectively.
Following the early death of Isabella's father in September 1506, her mother's mental health reportedly began to deteriorate. Isabella, along with her brother, Charles, and her sisters, Eleanor and Mary, was put into the care of her paternal aunt, Archduchess Margaret, governor of the Habsburg Netherlands, while the two other siblings, Ferdinand and Catherine, remained in Castile. Eleanor, Isabella, and Mary were educated together at their aunt's court in Mechelen.
Margaret, a wise, staunch Catholic, and politically experienced woman, played a significant role in shaping Isabella's upbringing. Under her aunt's care, Isabella received a comprehensive education from the learned renaissance humanists of the time. Her upbringing at the opulent court in Mechelen afforded Isabella the finest education of her time, and among her notable tutors were Juan Luis Vives and the later Pope Adrian VI, who was associated with the pre-Reformation movement known as the "Brethren of the Common Life." The Brethren were viewed favourably by Martin Luther and Philipp Melanchthon for their emphasis on Christian devotion and self-sacrifice. Many members of this movement later aligned with the Protestant cause in its divergence from the authority of the papal church.
In her education, Isabella received instruction from Vives, covering Greek and Latin studies. The curriculum included a focus on the Gospels, St. Paul's Epistles, and select portions of the Old Testament.
Margaret acted as a maternal figure to her brother's children, and in October 1507, she informed her father, Emperor Maximilian I, who closely followed and actively participated in matters concerning his grandchildren, of Isabella and Maria contracting measles, with Eleonora showing symptoms. Due to the contagious nature of the disease and winter conditions, Margaret and Archduke Charles opted to stay in Brussels rather than returning to Mechelen as initially intended.
The household of the imperial children was headed by First Chamberlain, Charles de Croy-Chimay and Grand Mistress (stewardess) Anna de Beaumont, a Spanish-Navarrese noblewoman of French origin, who had been Juana’s former lady-in-waiting, arriving in the Low Countries with the duchess in 1498.
Margaret heavily participated in the marriage negotiations of her nieces, including Isabella's. In 1509, Isabella's grandfather Emperor Maximilian proposed Henry of Navarre, son of John III, as a possible spouse, but the proposition was presumably dismissed by Margaret. By 1510, there were discussions about Isabel’s possible marriage to Charles II, Duke of Guelders, son of Adolf, Duke of Guelders. However, both Margaret and Maximilian harbored reservations about sending the young princess to Guelders, questioning the match's prestige. The Lord of Guelders held a lower rank as a duke, and their family's objective was to wed their daughters into royal houses.
Isabella's fortune, her succession rights, and her connections made her a valuable pawn in the royal marriage market. In 1513, Copenhagen hosted negotiations for the topic of the new King Christian II's marriage, leading to an agreement to pursue one of Philip the Beautiful's daughters. This alliance promised strategic advantages, creating kinship with the emperor and making King Christian the brother-in-law of Archduke Charles, a powerful figure in key Dutch cities. Furthermore, Habsburg-Austrian princesses were known for substantial dowries. King Christian enlisted the help of his uncle, Frederick III, Elector of Saxony, who, well-connected with the Emperor, inquired about suitable matches at the Imperial Court. In late October and early November, a national assembly in Viborg revisited the matrimonial issue, resolving to send an embassy to Emperor Maximilian for the formal proposal of Archduchess Isabella's hand. Bishop Gottschalk von Ahlefeldt, alongside Councilors Mogens Gjø and Albert Jepsen Ravensberg, was chosen to lead this envoy.
The king of Denmark had first intended to marry Isabella's eldest sister Eleanor of Austria, but the Habsburgs considered Eleanor too valuable for the throne of Denmark, because as the eldest sister, there was a likelihood that her descendants may succeed. Therefore, Isabella was selected for the Danish king. The Emperor expressed approval for the potential alliance with Denmark, a sentiment that found favor in the Low Countries. This alliance was viewed as a strategic opportunity to enhance trade access to the Baltic for merchants from Bruges and Amsterdam.
The envoyship reached the imperial court in Linz in early April, engaging in month-long negotiations culminating in the signing of a marriage contract on 29 April 1514. The substantial dowry amounted to 250,000 Rhenish gulden, approximately equal to 800 million DKK today (about 118 million USD), with contributions from Spain and the Burgundian territories. Princess Isabella was also assured an annual income of 25,000 Rhenish gulden.
On 11 July 1514, one week short of her 13th birthday, Isabella was married by proxy to King Christian II of Denmark with Emperor Maximilian I, her grandfather, standing in for the king. The Bishop of Cambrai, Jacob van Croÿ, presided over the wedding which was conducted at the Brussels Palace.