| 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 |
| Gregorian calendar | 843 DCCCXLIII |
| Ab urbe condita | 1596 |
| Armenian calendar | 292 ԹՎ ՄՂԲ |
| Assyrian calendar | 5593 |
| Balinese saka calendar | 764–765 |
| Bengali calendar | 250 |
| Berber calendar | 1793 |
| Buddhist calendar | 1387 |
| Burmese calendar | 205 |
| Byzantine calendar | 6351–6352 |
| Chinese calendar | 壬戌年 (Water Dog) 3539 or 3479 — to — 癸亥年 (Water Pig) 3540 or 3480 |
| Coptic calendar | 559–560 |
| Discordian calendar | 2009 |
| Ethiopian calendar | 835–836 |
| Hebrew calendar | 4603–4604 |
| Hindu calendars | |
| - Vikram Samvat | 899–900 |
| - Shaka Samvat | 764–765 |
| - Kali Yuga | 3943–3944 |
| Holocene calendar | 10843 |
| Iranian calendar | 221–222 |
| Islamic calendar | 228–229 |
| Japanese calendar | Jōwa 10 (承和１０年) |
| Javanese calendar | 740–741 |
| Julian calendar | 843 DCCCXLIII |
| Korean calendar | 3176 |
| Minguo calendar | 1069 before ROC 民前1069年 |
| Nanakshahi calendar | −625 |
| Seleucid era | 1154/1155 AG |
| Thai solar calendar | 1385–1386 |
| Tibetan calendar | 阳水狗年 (male Water-Dog) 969 or 588 or −184 — to — 阴水猪年 (female Water-Pig) 970 or 589 or −183 |
843 (DCCCXLIII) was a common year starting on Monday of the Julian calendar, the 843rd year of the Common Era (CE) and Anno Domini (AD) designations, the 843rd year of the 1st millennium, the 43rd year of the 9th century, and the 4th year of the 840s decade. As of the start of 843, the Gregorian calendar was 4 days ahead of the Julian calendar, which was the dominant calendar of the time.