842
| Years: 838 839 840 841 - 842 - 843 844 845 846 | |
| Decades: 810s 820s 830s - 840s - 850s 860s 870s | |
| Centuries: 8th century - 9th century - 10th century | |
Events
- Oath of Strasbourg - alliance of Louis the German and Charles the Bald against emperor Lothar - sworn and recorded in vernacular languages.
- Ramiro I succeeds Alfonso II as king of Asturias.
- Three year old Michael III succeeds Theophilus II as emperor of Byzantium.
- Uurad is succeeded by Bred, then Kineth.
- End of the reign of caliph Moqtasim.
- Charles the Bald marries Ermentrude.
Deaths
- January 5 - Al-Mu'tasim, Abbasid caliph
- Emperor Saga of Japan
- Alfonso II of Asturias
- Byzantine Emperor Theophilus II