921
| Years | 
|---|
| Millennium | 
| 1st millennium | 
| Centuries | 
| Decades | 
| Years | 
| 921 by topic | 
|---|
| Leaders | 
| Categories | 
| 
 | 
| Gregorian calendar | 921 CMXXI | 
| Ab urbe condita | 1674 | 
| Armenian calendar | 370 ԹՎ ՅՀ | 
| Assyrian calendar | 5671 | 
| Balinese saka calendar | 842–843 | 
| Bengali calendar | 327–328 | 
| Berber calendar | 1871 | 
| Buddhist calendar | 1465 | 
| Burmese calendar | 283 | 
| Byzantine calendar | 6429–6430 | 
| Chinese calendar | 庚辰年 (Metal Dragon) 3618 or 3411 — to — 辛巳年 (Metal Snake) 3619 or 3412 | 
| Coptic calendar | 637–638 | 
| Discordian calendar | 2087 | 
| Ethiopian calendar | 913–914 | 
| Hebrew calendar | 4681–4682 | 
| Hindu calendars | |
| - Vikram Samvat | 977–978 | 
| - Shaka Samvat | 842–843 | 
| - Kali Yuga | 4021–4022 | 
| Holocene calendar | 10921 | 
| Iranian calendar | 299–300 | 
| Islamic calendar | 308–309 | 
| Japanese calendar | Engi 21 (延喜21年) | 
| Javanese calendar | 820–821 | 
| Julian calendar | 921 CMXXI | 
| Korean calendar | 3254 | 
| Minguo calendar | 991 before ROC 民前991年 | 
| Nanakshahi calendar | −547 | 
| Seleucid era | 1232/1233 AG | 
| Thai solar calendar | 1463–1464 | 
| Tibetan calendar | 阳金龙年 (male Iron-Dragon) 1047 or 666 or −106 — to — 阴金蛇年 (female Iron-Snake) 1048 or 667 or −105 | 
Year 921 (CMXXI) was a common year starting on Monday of the Julian calendar.