|Centuries:||5th century – 6th century – 7th century|
|Decades:||490s 500s 510s – 520s – 530s 540s 550s|
|Years:||517 518 519 – 520 – 521 522 523|
|520 by topic|
|State leaders – Sovereign states|
|Birth and death categories|
|Births – Deaths|
|Establishment and disestablishment categories|
|Establishments – Disestablishments|
|Ab urbe condita||1273|
|Chinese calendar||己亥年 (Earth Pig)
3216 or 3156
— to —
庚子年 (Metal Rat)
3217 or 3157
|- Vikram Samvat||576–577|
|- Shaka Samvat||442–443|
|- Kali Yuga||3621–3622|
|Iranian calendar||102 BP – 101 BP|
|Islamic calendar||105 BH – 104 BH|
|Minguo calendar||1392 before ROC
|Seleucid era||831/832 AG|
|Thai solar calendar||1062–1063|
Year 520 (DXX) was a leap year starting on Wednesday (link will display the full calendar) of the Julian calendar. At the time, it was known as the Year of the Consulship of Rusticus and Vitalianus (or, less frequently, year 1273 Ab urbe condita). The denomination 520 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.
- Priscian, Latin grammarian, writes the Institutiones Grammaticae ("Grammatical Foundations"). In Constantinople he codifies this manuscript in 18 volumes that will be widely used through the Middle Ages. It provides the raw material for the field of speculative grammar.
- July – Vitalian, Byzantine general, becomes consul and is shortly later murdered, probably on the orders of Justinian. He is the nephew and heir-apparent of emperor Justin I.
- King Pabo Post Prydain of the Pennines (Northern England) abdicates his throne and divides the kingdom between his two sons. He retires, as a hermit, to Anglesey.
- The Kingdom of East Anglia is formed, by the merging of the English counties of Norfolk and Suffolk and perhaps the eastern part of The Fens (approximate date).
- King Budic II returns to Cornouaille (Brittany) to claim the Breton throne (approximate date).
- The Ostrogothic ruler Theodoric the Great builds the Mausoleum of Theodoric as his future tomb in Ravenna (Italy).
- Bodhidharma, Buddhist monk, arrives in Luoyang. He spreads Buddhism and travels to the northern Chinese kingdom of Wei to the Shaolin Monastery.
- February 25 – Epiphanius is elected patriarch of Constantinople by the Byzantine emperor Justin I.
- The construction of the Basilica of San Vitale in Ravenna, is started (approximate date).
- Hou Andu, general of the Chen Dynasty (d. 563)
- Justin II, emperor of the Byzantine Empire (d. 578)
- Malo, Welsh bishop (approximate date)
- Martin of Braga, missionary and archbishop (d. 580)
- Pope Pelagius II, pope of Rome (d. 589)
- Radegund, Frankish princess (approx.)
- Zuhayr bin Abi Sulma, Arabian poet (approx.)
- Abbán, Irish cult leader and saint (approx.)
- Ardgal mac Conaill, king of Uisneach (Ireland)
- Isidore of Alexandria, Neoplatonist philosopher (approximate date)
- January 19 – John of Cappadocia, patriarch of Constantinople
- Maximinus, Frankish abbot and saint (approximate date)
- July – Vitalian, Byzantine general and consul
- Zu Gengzhi, Chinese mathematician (approx.)