The 1850s decade ran from January 1, 1850, to December 31, 1859.
- Crimean War (1854–56) fought between Imperial Russia and an alliance consisting of the United Kingdom of Great Britain and Ireland, the Second French Empire, the Kingdom of Sardinia and the Ottoman Empire. The majority of the conflict takes place around Crimea, on the northern coasts of the Black Sea.
- On 8 October 1856, the Second Opium War between several western powers and China begins with the Arrow Incident on the Pearl River.
- Second War of Italian Independence (1859), additionally known as Franco-Austrian War, or Austro-Sardinian War.
- The Indian Mutiny: revolt against British colonial rule in India
- Bleeding Kansas (1854–59): battles erupt in Kansas Territory between proslavery and "Free-State" settlers, directly precipitating the American Civil War.
- Taiping Rebellion (1851–64) in Qing China.
Prominent political events
- Moldavia and Wallachia are unified and form Romania.
- Gideon T. Stewart attempts to create a Prohibition Party.
- Dissolution of the Mughal Empire by the British.
The 1850s were marked by several notable assassinations and assassination attempts:
- Eight were killed and 142 wounded in Paris in a failed assassination attempt on Napoleon III, Emperor of the French (1858).
- Charles Darwin publishes The Origin of Species, putting forward the theory of evolution by natural selection in 1859
- Epidemiology begins when John Snow traces the source of an outbreak of cholera in London to a contaminated water pump.
- Discovery of Neanderthal fossils in Neanderthal, Germany
- Solar flares detected by Richard Christopher Carrington
- Distinction between coats and jackets begins to blur
- Production of steel revolutionised by invention of the Bessemer process
- Benjamin Silliman fractionates petroleum by distillation for the first time
- First transpacific telegraph cable laid
- First safety elevator installed by Elisha Otis
- Railroads begin to supplant canals in the United States as a primary means of transporting goods.
- First commercially successful sewing machine made by Isaac Singer
- The word girlfriend first appears in writing in 1855.
- The word boyfriend first appears in writing in 1856.
- Charles Dickens publishes Bleak House, Hard Times, Little Dorrit and A Tale of Two Cities
- Nathaniel Hawthorne publishes The Scarlet Letter in 1850
- Herman Melville publishes Bartleby, the Scrivener in 1853
- Padshah Bahadur Shah Zafar (Mughal Empire)
- Emperor Franz Josef (Austria-Hungary)
- Emperor Napoleon III (Second French Empire)
- King Frederick William IV (Germany)
- Pope Pius IX
- Queen Maria II (Portugal)
- King Peter V (Portugal)
- Emperor Nicholas I (Russia)
- Emperor Alexander II (Russia)
- Queen Isabella II (Spain)
- Queen Victoria, (United Kingdom of Great Britain and Ireland)
- Prime Minister Lord John Russell (United Kingdom of Great Britain and Ireland)
- Prime Minister Lord Aberdeen (United Kingdom of Great Britain and Ireland)
- Prime Minister Lord Palmerston (United Kingdom of Great Britain and Ireland)
- President Zachary Taylor (United States)
- President Millard Fillmore (United States)
- President Franklin Pierce (United States)
- President James Buchanan (United States)
- Naser al-Din Shah Qajar of Qajar dynasty (Persia)