Back Anyos 840 AN عقد 840 Arabic عوام 840 ARY عقد 840 ARZ Década del 840 AST 840-an BAN 840-я Byelorussian 840-я BE-X-OLD ৮৪০-এর দশক Bengali/Bangla Bloavezhioù 840 Breton
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.
| Millennium: | 1st millennium |
| 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 |