July 27 - Mikhail Lermontov, Russian author (b. 1814)
August 24 - Theodore Edward Hook, English author (b. 1788)
September 9 - A. P. de Candolle, Swiss botanist (b. 1778)
January 20 - Hong Kong Island is occupied by the British.
January 26 - The United Kingdom formally occupies Hong Kong, which China later formally ceded.
January 30 - A fire destroys two-thirds of Mayagüez, Puerto Rico.
February 18 - The first ongoing filibuster in the United States Senate begins and lasts until March 11.
March 9 - The Supreme Court of the United States rules in the Amistad case, concerning captive Africans who seized control of the slave-trading ship carrying them: the court rules that they had been taken into slavery illegally.
April 4 - William Henry Harrison dies of pneumonia becoming the first President of the United States to die in office and the one with the shortest term served.
May 11 - Lt. Charles Wilkes lands at Fort Nisqually in Puget Sound.
June 28 - The Théâtre de l'Académie Royale de Musique in Paris premieres the ballet Giselle
August 16 - U.S. President John Tyler vetoes a bill which called for the re-establishment of the Second Bank of the United States. Enraged Whig Party members riot outside the White House in the most violent demonstration on White House grounds in U.S. history.
September 24 - The Sultan of Brunei cedes Sarawak to Britain.
October 16 - Queen's University is founded in Kingston, Ontario, Canada.
November 13 - James Braid first sees a demonstration of animal magnetism, which leads to his study of the subject he eventually calls hypnosis.