Year 538 (DXXXVIII) 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 Iohannes without colleague (or, less frequently, year 1291 Ab urbe condita). The denomination 538 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.
|Ab urbe condita||1291|
|Balinese saka calendar||459–460|
|Chinese calendar||丁巳年 (Fire Snake)|
3234 or 3174
— to —
戊午年 (Earth Horse)
3235 or 3175
|- Vikram Samvat||594–595|
|- Shaka Samvat||459–460|
|- Kali Yuga||3638–3639|
|Iranian calendar||84 BP – 83 BP|
|Islamic calendar||87 BH – 86 BH|
|Minguo calendar||1374 before ROC|
|Seleucid era||849/850 AG|
|Thai solar calendar||1080–1081|
664 or 283 or −489
— to —
665 or 284 or −488
- March 12 – Siege of Rome: King Vitiges of the Ostrogoths ends his siege (after 374 days) and abandons Rome. He retreats with his Gothic army northeast along the Via Flaminia.
- Belisarius attacks the Goths when they have crossed the Milvian Bridge. After fierce resistance, Vitiges routs in panic, and many are slain or drowned in the river.
- Gothic War: Vitiges strengthens the garrisons of various towns and besieges Ariminum. Byzantine forces under the Armenian general Narses arrive at Picenum.
- April – Belisarius secures Liguria, Mediolanum (modern Milan) and Ariminum, but disagreements, especially with Narses, leads to disunity in the Byzantine army.
- Summer – King Theudebert I sends a small Frankish force across the Alps, and defeats the Goths and Byzantines at the River Po. Belisarius retreats to Tuscany.
- Sittas, Byzantine general, suppresses a revolt in Armenia in protest against heavy taxation. During the campaign he is killed by Artabanes, leader of the revolt.
- King Cuneglas of Rhos abandons his wife in favour of his sister-in-law, a nun who he drags from her convent (approximate date).
- Gabrán mac Domangairt becomes king of Dál Riata (Scotland).
- King Seong of Paekche (Korea) moves the capital from Ungjin (present-day Gongju) further south to Sabi (present-day Buyeo County), on the Geum River. He sends a diplomatic mission that formally introduces Buddhism to the Japanese imperial court (see also 552).
- The Kofun period ends and the Asuka period, the second part of the Yamato period in Japan, begins.
- As a result of persecutions by the Byzantine Empire, Monophysite Christians establish the Coptic Church in Alexandria (approximate date).
- The Third Council of Orléans takes place and prohibits rural labor on Sunday.
- The first time since Emperor Justinian's decree of 533 that John became the Bishop of Rome, Chief Bishop of all the churches. The supremacy of the Bishop of Rome over the Church could actually be implemented by Vigilius.