840s

The 840s started on 1 January 840 and ended on 31 December 849. It is distinct from the decade known as the 85th decade which began on January 1, 841 and ended on December 31, 850.
 Events 
 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.

 Important people 
 Charles the Bald
 Louis the German
 Lothair I
 Kenneth I of Scotland
 Ragnar Lodbrok