| Millennium: | 1st millennium |
|---|---|
| Centuries: | |
| Decades: | |
| Years: |
| Gregorian calendar | 803 DCCCIII |
| Ab urbe condita | 1556 |
| Armenian calendar | 252 ԹՎ ՄԾԲ |
| Assyrian calendar | 5553 |
| Bengali calendar | 210 |
| Berber calendar | 1753 |
| Buddhist calendar | 1347 |
| Burmese calendar | 165 |
| Byzantine calendar | 6311–6312 |
| Chinese calendar |
壬午年 (Water Horse) 3499 or 3439 — to — 癸未年 (Water Goat) 3500 or 3440 |
| Coptic calendar | 519–520 |
| Discordian calendar | 1969 |
| Ethiopian calendar | 795–796 |
| Hebrew calendar | 4563–4564 |
| Hindu calendars | |
| - Vikram Samvat | 859–860 |
| - Shaka Samvat | 724–725 |
| - Kali Yuga | 3903–3904 |
| Holocene calendar | 10803 |
| Iranian calendar | 181–182 |
| Islamic calendar | 187–188 |
| Japanese calendar |
Enryaku 22 (延暦22年) |
| Javanese calendar | 698–699 |
| Julian calendar | 803 DCCCIII |
| Korean calendar | 3136 |
| Minguo calendar | 1109 before ROC 民前1109年 |
| Nanakshahi calendar | −665 |
| Seleucid era | 1114/1115 AG |
| Thai solar calendar | 1345–1346 |
Year 803 (DCCCIII) was a common year starting on Sunday (link will display the full calendar) of the Julian calendar.