1251
| Years | 
|---|
| Millennium | 
| 2nd millennium | 
| Centuries | 
| Decades | 
| Years | 
| 1251 by topic | 
|---|
| Leaders | 
| 
 | 
| Birth and death categories | 
| Births – Deaths | 
| Establishments and disestablishments categories | 
| Establishments – Disestablishments | 
| Art and literature | 
| 1251 in poetry | 
| Gregorian calendar | 1251 MCCLI | 
| Ab urbe condita | 2004 | 
| Armenian calendar | 700 ԹՎ Չ | 
| Assyrian calendar | 6001 | 
| Balinese saka calendar | 1172–1173 | 
| Bengali calendar | 657–658 | 
| Berber calendar | 2201 | 
| English Regnal year | 35 Hen. 3 – 36 Hen. 3 | 
| Buddhist calendar | 1795 | 
| Burmese calendar | 613 | 
| Byzantine calendar | 6759–6760 | 
| Chinese calendar | 庚戌年 (Metal Dog) 3948 or 3741 — to — 辛亥年 (Metal Pig) 3949 or 3742 | 
| Coptic calendar | 967–968 | 
| Discordian calendar | 2417 | 
| Ethiopian calendar | 1243–1244 | 
| Hebrew calendar | 5011–5012 | 
| Hindu calendars | |
| - Vikram Samvat | 1307–1308 | 
| - Shaka Samvat | 1172–1173 | 
| - Kali Yuga | 4351–4352 | 
| Holocene calendar | 11251 | 
| Igbo calendar | 251–252 | 
| Iranian calendar | 629–630 | 
| Islamic calendar | 648–649 | 
| Japanese calendar | Kenchō 3 (建長3年) | 
| Javanese calendar | 1160–1161 | 
| Julian calendar | 1251 MCCLI | 
| Korean calendar | 3584 | 
| Minguo calendar | 661 before ROC 民前661年 | 
| Nanakshahi calendar | −217 | 
| Thai solar calendar | 1793–1794 | 
| Tibetan calendar | 阳金狗年 (male Iron-Dog) 1377 or 996 or 224 — to — 阴金猪年 (female Iron-Pig) 1378 or 997 or 225 | 
Year 1251 (MCCLI) was a common year starting on Sunday of the Julian calendar.