| Millennium: | 1st millennium |
|---|---|
| Centuries: | |
| Decades: | |
| Years: |
| Gregorian calendar | 851 DCCCLI |
| Ab urbe condita | 1604 |
| Armenian calendar | 300 ԹՎ Յ |
| Assyrian calendar | 5601 |
| Bengali calendar | 258 |
| Berber calendar | 1801 |
| Buddhist calendar | 1395 |
| Burmese calendar | 213 |
| Byzantine calendar | 6359–6360 |
| Chinese calendar |
庚午年 (Metal Horse) 3547 or 3487 — to — 辛未年 (Metal Goat) 3548 or 3488 |
| Coptic calendar | 567–568 |
| Discordian calendar | 2017 |
| Ethiopian calendar | 843–844 |
| Hebrew calendar | 4611–4612 |
| Hindu calendars | |
| - Vikram Samvat | 907–908 |
| - Shaka Samvat | 772–773 |
| - Kali Yuga | 3951–3952 |
| Holocene calendar | 10851 |
| Iranian calendar | 229–230 |
| Islamic calendar | 236–237 |
| Japanese calendar |
Kashō 4 / Ninju 1 (仁寿元年) |
| Javanese calendar | 748–749 |
| Julian calendar | 851 DCCCLI |
| Korean calendar | 3184 |
| Minguo calendar | 1061 before ROC 民前1061年 |
| Nanakshahi calendar | −617 |
| Seleucid era | 1162/1163 AG |
| Thai solar calendar | 1393–1394 |
Year 851 (DCCCLI) was a common year starting on Thursday (link will display the full calendar) of the Julian calendar.