The 840s started on 1 January 840 and ended on 31 December 849.
|Centuries:||8th century – 9th century – 10th century|
|Decades:||810s 820s 830s – 840s – 850s 860s 870s|
|Years:||840 841 842 843 844 845 846 847 848 849|
|Categories:||Births – Deaths – Architecture|
Establishments – Disestablishments
- After the death of Louis the Pious, his sons Charles the Bald, Louis the German and Lothair II of Lotharingia fight about the division of the empire until the treaty of Verdun (843).
- Viking raid of Western Francia (France) (845).
- Vikings conquer Frisia, the present Netherlands and the German North Sea coastline.
- Beginning of Arab domination on Taranto, which will last until 880.