1542

January–June

• February 2 - Battle of Baçente: The Portuguese under Cristóvão da Gama capture a Muslim-occupied hillfort in northern Ethiopia.
• February 13 - Catherine Howard, the fifth wife of Henry VIII of England, is executed for adultery.
• February 14 - Guadalajara, Mexico, is founded by the Spaniards after three previous attempts failed, due to aggressive opposition from local tribes.
• March 8 - Antoine Escalin des Eymars, the French ambassador, returns from Constantinople, with promises of Ottoman aid in a war against Charles V, Holy Roman Emperor.
• March - Renyin palace rebellion: A group of Ming Dynasty palace women fail to murder the Jiajing Emperor, and are executed by slow-slicing.
• April 4-16 - Battle of Jarte in Ethiopia: The Portuguese under Cristóvão da Gama encounter the army of Imam Ahmad Gragn, and inflict upon him two successive defeats.
• May 19 - The Prome Kingdom, in modern-day central Burma, is conquered by the Taungoo Dynasty.

  July–December

• July 12 - Charles V, Holy Roman Emperor declares war on King Francis I of France. This time King Henry VIII of England is allied to the Emperor, while James V of Scotland and Sultan Suleiman I are allied to the French.
• August - Battle of the Hill of the Jews: During the rainy season, Cristóvão da Gama captures a strategic position and many badly-needed horses.
• August 24 - Battle of Haddon Rig: Scotland defeats England.
• August 27 - Citizens of Hildesheim in the Holy Roman Empire profess themselves to the Lutheran teachings. As a pledge owner, the city provides for the carrying out of the Protestant Reformation in the city and Peine. Priests from the localities of Clauen, Hohenhameln, Soßmar, Schmedenstedt, Lengede and Rosenthal resume their offices in the interest of the Reformation.
• August 28 - Battle of Wofla in Ethiopia: Reinforced with at least 600 arquebusiers and cavalry, Imam Ahmad Gragn attacks the Portuguese camp. The Portuguese are scattered; Cristóvão da Gama is captured and executed.
• September 4 - The earliest recorded Preston Guild Court is held in Lancashire, England, in the modern sequence, which lasts unbroken until 1922.
• September 28 - Portuguese explorer Juan Rodríguez Cabrillo lands in what is now San Diego Bay, and names it "San Miguel"; it will later become the city of San Diego.
• October 7 - Cabrillo becomes the first European to set foot on Santa Catalina Island, California.
• November 24 - Battle of Solway Moss: An English army invades Scotland, and defeats a Scottish army.
• December 14 - Mary, Queen of Scots, becomes queen regnant one week after the death of her father, James V of Scotland.

  Date unknown

• The first contact of Japan with the West occurs when a Portuguese ship, blown off its course to China, lands Fernão Mendes Pinto, Francisco Zeimoto and António Mota in Japan..
• Pope Paul III establishes the Holy Office, with jurisdiction over the Roman Inquisition.
• Bartolomé de las Casas completes A Short Account of the Destruction of the Indies, which will be published in 1552.