804
| Years | 
|---|
| Millennium | 
| 1st millennium | 
| Centuries | 
| Decades | 
| Years | 
| 804 by topic | 
|---|
| Leaders | 
| Categories | 
| 
 | 
| Gregorian calendar | 804 DCCCIV | 
| Ab urbe condita | 1557 | 
| Armenian calendar | 253 ԹՎ ՄԾԳ | 
| Assyrian calendar | 5554 | 
| Balinese saka calendar | 725–726 | 
| Bengali calendar | 210–211 | 
| Berber calendar | 1754 | 
| Buddhist calendar | 1348 | 
| Burmese calendar | 166 | 
| Byzantine calendar | 6312–6313 | 
| Chinese calendar | 癸未年 (Water Goat) 3501 or 3294 — to — 甲申年 (Wood Monkey) 3502 or 3295 | 
| Coptic calendar | 520–521 | 
| Discordian calendar | 1970 | 
| Ethiopian calendar | 796–797 | 
| Hebrew calendar | 4564–4565 | 
| Hindu calendars | |
| - Vikram Samvat | 860–861 | 
| - Shaka Samvat | 725–726 | 
| - Kali Yuga | 3904–3905 | 
| Holocene calendar | 10804 | 
| Iranian calendar | 182–183 | 
| Islamic calendar | 188–189 | 
| Japanese calendar | Enryaku 23 (延暦23年) | 
| Javanese calendar | 699–700 | 
| Julian calendar | 804 DCCCIV | 
| Korean calendar | 3137 | 
| Minguo calendar | 1108 before ROC 民前1108年 | 
| Nanakshahi calendar | −664 | 
| Seleucid era | 1115/1116 AG | 
| Thai solar calendar | 1346–1347 | 
| Tibetan calendar | 阴水羊年 (female Water-Goat) 930 or 549 or −223 — to — 阳木猴年 (male Wood-Monkey) 931 or 550 or −222 | 
Year 804 (DCCCIV) was a leap year starting on Monday of the Julian calendar.