|Covid-19|January 13 – At Västerås, the estates of Sweden swear loyalty to king Gustav Vasa and to his heirs, ending the traditional electoral monarchy in Sweden. Gustav subsequently signs an alliance with the Kingdom of France.
April 11 – Battle of Ceresole: French forces under the Comte d'Enghien defeat forces of the Holy Roman Empire under the Marques Del Vasto near Turin.
May – Charles V, Holy Roman Emperor, again invades eastern France.
May 3 – Edward Seymour, Earl of Hertford, with an English army captures Leith and Edinburgh from the Kingdom of Scotland.
June 19–August 18 – Troops of the Holy Roman Empire besiege Saint-Dizier in eastern France.
July – Battle of the Shirts: The Clan Fraser of Lovat and Macdonalds of Clan Ranald fight over a disputed chiefship in Scotland; reportedly, five Frasers and eight Macdonalds survive.
July 19–September 14 – First Siege of Boulogne: King Henry VIII of England besieges and captures Boulogne in northern France during the Italian War of 1542–46.
September 18 – Peace of Crépy: Peace is declared between Charles V, Holy Roman Emperor, and Francis I of France. The war between France and England continues.
September 22 – Captain Juan Bautista Pastene leads the first European expedition to the estuary of Valdivia, Chile and Corral Bay.
October 9 – Second Siege of Boulogne: French forces under the Dauphin assault Boulogne, but are ultimately unsuccessful.
Mongols burn the suburbs of Peking in China.
The University of Königsberg is founded.
Orto botanico di Pisa botanical garden established by Cosimo I de' Medici, Grand Duke of Tuscany, in Italy under the direction of botanist Luca Ghini, who also creates the first herbarium.
Rats make their first appearance in North America.
Portuguese explorers encounter the island of Taiwan and call it Ilha Formosa ("Beautiful Island").
January 19 – King Francis II of France (d. 1560)
January 24 – Gillis van Coninxloo, painter (d. 1607)
February 1 – Mogami Yoshiaki, Daimyo of the Yamagata domain (d. 1614)
February 3 – César de Bus, French Catholic priest (d. 1607)
March 11 – Torquato Tasso, Italian poet (d. 1595)
April – Thomas Fleming, English judge (d. 1613)
April 20 – Renata of Lorraine, Duchess consort of Bavaria (d. 1602)
May 24 – William Gilbert, English scientist and astronomer (d. 1603)
July 14 – Henry Compton, 1st Baron Compton, English politician (d. 1589)
August 9 – Bogislaw XIII, Duke of Pomerania (d. 1606)
September 1 – John Gordon, Scottish bishop (d. 1619)
September 29 – Giovanni de' Medici, Catholic cardinal (d. 1562)
November 1 – Hasan Kafi Pruščak, Bosnian scholar and judge (d. 1615)
November 15 – Dorothea Susanne of Simmern, Duchess of Saxe-Weimar (d. 1592)
December 23 – Anna of Saxony, only child and heiress of Maurice, Elector of Saxony (d. 1577)
Richard Bancroft, Archbishop of Canterbury (d. 1610)
Thomas Hobson, English carrier and origin of the phrase "Hobson's choice" (d. 1631)
Ikeda Tomomasa, Japanese military commander (d. 1603)
Maddalena Casulana, Italian composer, lutenist and singer (d. 1590)
Sanada Masayuki, Japanese military leader (d. 1611)
George Whetstone, English writer (d. 1587)
March 22 – Johannes Magnus, last Catholic Archbishop of Sweden (b. 1488)
April 30 – Thomas Audley, Lord Chancellor of England (b. 1488)
June 14 – Antoine, Duke of Lorraine (b. 1489)
July 15 – René of Châlon, Prince of the House of Orange (b. 1519)
September 10 – Clément Marot, French poet (b. 1496)
September 25 – Valerius Cordus, German physician and scientist (b. 1515)
December 9 – Teofilo Folengo, Italian poet (b. 1491)
Ulick na gCeann Burke, 1st Earl of Clanricarde
Chen Chun, Chinese painter (b. 1483)
Nilakantha Somayaji, Indian mathematician and astronomer (b. 1444)
Manco Inca Yupanqui, ruler of the Inca (b. 1516)
Bonaventure des Périers, French author (b. 1500)
Year 1544 (MDXLIV) was a leap year starting on Tuesday (link will display the full calendar) of the Julian calendar.