| Centuries: |
18th century - 19th century - 20th century
| Decades: |
1810s 1820s 1830s - 1840s - 1850s 1860s 1870s
1840 1841 1842 1843 1844 1845 1846 1847 1848 1849
- First signing of the Treaty of Waitangi (Te Tiriti o Waitangi) on February 6, 1840 at Waitangi New Zealand. The treaty between the British Crown and Maori made New Zealand a British colony and is considered the founding point of modern New Zealand.
- Introduction of the postage stamp. The first of them is Penny Black, issued by the United Kingdom of Great Britain and Ireland on May 1, 1840.
- Mexican-American War (1846 - 1848) fought between Mexico and the United States of America. The later emerges victorious and gains undisputed control over Texas while annexing portions of Arizona, California and New Mexico.
- Wave of revolutions in Europe. Collectively known as the Revolution of 1848.
- Karl Marx writes The Communist Manifesto, first published on February 21, 1848.
- Emperor Ferdinand I (Austria)
- Chancellor Klemens Wenzel von Metternich (Austria)
- Emperor Franz Josef (Austria-Hungary)
- King Louis-Philippe (France)
- Pope Gregory XVI
- Pope Pius IX
- Emperor Nicholas I (Russia)
- Queen Victoria (United Kingdom)
- Prime Minister Lord Melbourne (United Kingdom)
- Prime Minister Sir Robert Peel (United Kingdom)
- Prime Minister Lord John Russell (United Kingdom)
- President Martin Van Buren (United States)
- President John Tyler (United States)
- President James Knox Polk (United States)