| Centuries: | 5th century · 6th century · 7th century |
| Decades: | 490s 500s 510s 520s 530s 540s 550s |
| Years: | 518 519 520 521 522 523 524 |
| 521 by topic | |
| Politics | |
| State leaders – Sovereign states | |
| Birth and death categories | |
| Births – Deaths | |
| Establishment and disestablishment categories | |
| Establishments – Disestablishments | |
| Gregorian calendar | 521 DXXI |
| Ab urbe condita | 1274 |
| Armenian calendar | N/A |
| Bahá'í calendar | -1323 – -1322 |
| Bengali calendar | -72 |
| Berber calendar | 1471 |
| Buddhist calendar | 1065 |
| Burmese calendar | -117 |
| Byzantine calendar | 6029 – 6030 |
| Chinese calendar | 庚子年十二月初八日 (3157/3217-12-8) — to —
辛丑年十一月十七日(3158/3218-11-17) |
| Coptic calendar | 237 – 238 |
| Ethiopian calendar | 513 – 514 |
| Hebrew calendar | 4281 – 4282 |
| Hindu calendars | |
| - Bikram Samwat | 577 – 578 |
| - Shaka Samvat | 443 – 444 |
| - Kali Yuga | 3622 – 3623 |
| Holocene calendar | 10521 |
| Iranian calendar | 101 BP – 100 BP |
| Islamic calendar | 104 BH – 103 BH |
| Japanese calendar | |
| Korean calendar | 2854 |
| Thai solar calendar | 1064 |