Upon her husband's death following the Battle of Mohács in 1526, Queen Mary governed Hungary as regent in the name of the new king, her brother, Ferdinand I.

Following the death of their aunt Margaret in 1530, Mary was asked by her eldest brother, Charles V, Holy Roman Emperor, to assume the governance of the Netherlands and guardianship over their nieces, Dorothea and Christina of Denmark.

Although she never enjoyed governing and asked for permission to resign several times, the Queen succeeded in creating a unity between the provinces, securing for them a measure of independence from both France and the Holy Roman Empire[1] as well as in creating of a permanent navy for Netherlands alongside Maximilian of Burgundy and Cornelis de Schepper.

Born in Brussels on 15 September 1505, between ten and eleven in the morning, Archduchess Mary of Austria was the fifth child of Philip the Handsome, Duke of Burgundy, and Queen Joanna of Castile.

On 20 September, she was baptized by Nicolas Le Ruistre, Bishop of Arras, and named after her paternal grandmother, Mary of Burgundy, who had died in 1482.

At the same time, Louis' sister Anne was betrothed to an as yet unspecified brother of Mary, with Emperor Maximilian acting as proxy.

Despite her brother Ferdinand's strong disapproval, Luther's teachings held great appeal for Mary during her marriage and even more for her sister Isabella and her brother-in-law King Christian II of Denmark.

The return was lukewarm,[10] but historian Helmut Georg Koenigsberger considers Mary's reputation for sympathy with Lutheranism to be "much-exaggerated".

Mary tried to cooperate with her brother Ferdinand in organizing a Hungarian defence against the Ottoman Empire, while at the same time consolidating Habsburg influence.

She was much more vigorous and spiritually stronger than Louis – the Hungarians realized this themselves and criticized their king – but the fact she relied on non-Hungarian advisors cost her sympathy.

Mary took a vow to never remarry and always wore the heart-shaped medallion worn by her husband in the fatal Battle of Mohács.

In 1530 Charles again suggested that she should remarry; he proposed to arrange a marriage to Frederick II, Elector Palatine, who had unsuccessfully courted Mary's sister Eleanor sixteen years before.

Archduchess Margaret died on 1 December the next year, leaving the position of Governor of the Seventeen Provinces in the Netherlands vacant.

[15] On 3 January 1531, Mary's older brother, Holy Roman Emperor Charles V, requested that she assume the regency of the Netherlands.

Charles was ruling a vast empire and was constantly in need of reliable family members who could govern his remote territories in his name.

[16]Mary served as regent of the Netherlands so well that Charles forced her to retain the post and granted her more powers than their aunt had enjoyed.

[4] Yet, upon leaving the States General in October 1531, Charles gave her a warning, saying that if his parent, wife, child or sibling became a follower of Luther, he would consider them his greatest enemy.

A 1551 petition by Antwerp merchants to the Habsburg government claimed that Scottish pirates and others, over the course of eight to ten years, had taken ships and goods that were worth about 1,600,000 Holland pounds.

Many were in favor of safe-conducts, supposedly cheaper and more effective than building up naval armaments, but the Queen refused to negotiate with a weak Scottish government.

Despite a firm sentiment against money for warships, Mary acted resolutely and issued orders forbidding all herring buses or merchantmen from sailing until the three fishing provinces could formulate an acceptable plan for naval defense.

Under her pressure, the provinces agreed to create a common Netherlands war fleet, but differences were only completely worked out in the very last years of her government.

James D.Tracy comments that "The development of this new strategy for naval defense was no small accomplishment, but most of the credit should go to the leadership provided by Mary of Hungary and her officials".

[28] Mary, the Admiral Maximilian of Burgundy and the Councillor Cornelis de Schepper were the team behind the professionalization process that characterized the Low Countries' maritime policy in the 1550–1555 period.

[29] The Queen had to mediate between her brothers in 1555, when Charles decided to abdicate as emperor and leave the government of the Netherlands to his son Philip, despite Ferdinand's objections.

[30] Although she repeatedly assured her brother that she had no intention of occupying herself with the affairs of state, Mary offered to become adviser to her niece Joanna, who was serving as regent for Philip.

Charles told her that he wanted her to resume regency in the Netherlands, and promised a home and a large income, but Mary declined the offer.

[37][38] When Joanna visited her, Mary was still determined to fulfill the promise she had given to Charles and assume the regency in the Netherlands, but she was weak and feverish.

[40] Mary was a keen art collector, and owned several important masterpieces of Early Netherlandish painting as well as more contemporary works.

Her portraits, letters, and comments by her contemporaries do not assign her the easy Burgundian charm possessed by her grandmother, Duchess Mary of Burgundy, and her aunt Margaret.

[45] What made her perceived as masculine (and usually attracted criticism as going beyond "acceptable female behavior") was "her authoritarian manner, her overly public life and her 'masculine' activities".