|Centuries:||1st century BC – 1st century – 2nd century|
|Decades:||20s 30s 40s – 50s – 60s 70s 80s|
|Years:||48 49 50 – 51 – 52 53 54|
|51 by topic|
|State leaders – Sovereign states|
|Birth and death categories|
|Births – Deaths|
|Establishment and disestablishment categories|
|Establishments – Disestablishments|
|Ab urbe condita||804|
|Bahá'í calendar||−1793 – −1792|
|English Regnal year||N/A|
|Chinese calendar||庚戌年 (Metal Dog)
2747 or 2687
— to —
辛亥年 (Metal Pig)
2748 or 2688
|Coptic calendar||−233 – −232|
|- Vikram Samvat||107–108|
|- Shaka Samvat||N/A|
|- Kali Yuga||3152–3153|
|Igbo calendar||−949 – −948|
|Iranian calendar||571 BP – 570 BP|
|Islamic calendar||589 BH – 588 BH|
|Minguo calendar||1861 before ROC
|Thai solar calendar||594|
|Wikimedia Commons has media related to 51.|
Year 51 (LI) was a common year starting on Friday (link will display the full calendar) of the Julian calendar. At the time, it was known as the Year of the Consulship of Caesar and Scipio (or, less frequently, year 804 Ab urbe condita). The denomination 51 for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years.
- Emperor Claudius and Titus Flavius Vespasianus are Roman Consuls.
- Burrus, praetorian prefect (51–62 AD), is charged by Seneca with the education of Nero.
- In Britain, governor Publius Ostorius Scapula defeats Caratacus and the Silures in the territory of the Ordovices in central Wales. Caratacus seeks sanctuary with Cartimandua, queen of the Brigantes in northern England, but she is a Roman ally and hands him over to Ostorius. Despite the defeat, the Silures continue to fight.
- The captured Caratacus is exhibited in chains in Claudius' triumph in Rome, but his dignified demeanour persuades the emperor to spare his life and allow his family to live free in the capital for short period of time.
- Vonones II died after a few months he ascended to the throne, his son Vologases I of Parthia becomes ruler of the Parthian Empire.
- Paul of Tarsus begins his second mission (approximate date).
- The New Testament book 1 Thessalonians is written (possible date).
- In the Epistle to the Galatians, Paul supports the separation of Christianity and Judaism.
- Lucius Vitellius the Elder, Roman consul and Governor of Syria (b. 5 BC)
- Gotarzes II of Parthia, ruler of the Parthian Empire
- Vonones II of Parthia, ruler of the Parthian Empire