Centuries:	8th century - 9th century - 10th century
Decades:	810s  820s  830s  - 840s -  850s  860s  870s
Years:	837 838 839 - 840 - 841 842 843

840 by topic v • d • e

Politics

State leaders - Sovereign states

Birth and death categories

Births - Deaths

Establishment and disestablishment categories

Establishments - Disestablishments

840 in other calendars

Gregorian calendar	840 DCCCXL
Ab urbe condita	1593
Armenian calendar	289 ԹՎ ՄՁԹ
Bahá'í calendar	-1004 – -1003
Berber calendar	1790
Buddhist calendar	1384
Burmese calendar	202
Byzantine calendar	6348 – 6349
Chinese calendar	己未年十一月廿三日 (3476/3536-11-23) — to — 庚申年十二月初四日 (3477/3537-12-4)
Coptic calendar	556 – 557
Ethiopian calendar	832 – 833
Hebrew calendar	4600 – 4601
Hindu calendars
- Vikram Samvat	895 – 896
- Shaka Samvat	762 – 763
- Kali Yuga	3941 – 3942
Holocene calendar	10840
Iranian calendar	218 – 219
Islamic calendar	225 – 226
Japanese calendar
Korean calendar	3173
Thai solar calendar	1383
v • d • e

Events

By Place

Europe

• After the death of Louis the Pious, his sons Lothar, Charles the Bald and Louis the German fight over the division of the Holy Roman Empire, with Lothar succeeding as Emperor.
• Dublin, Ireland is founded by the Vikings.

Asia

• Tang Wu Zong succeeds Tang Wen Zong as emperor of China.

Deaths

• June 20 — Louis the Pious, King of the Franks, Emperor of the Holy Roman Empire (b. 778)
• Emperor Junna of Japan (b. 786)
• Wiglaf, King of Mercia
• Emperor Wenzong of Tang