|819 by topic|
|Ab urbe condita||1572|
|Balinese saka calendar||740–741|
|Chinese calendar||戊戌年 (Earth Dog)|
3515 or 3455
— to —
己亥年 (Earth Pig)
3516 or 3456
|- Vikram Samvat||875–876|
|- Shaka Samvat||740–741|
|- Kali Yuga||3919–3920|
|Japanese calendar||Kōnin 10|
|Minguo calendar||1093 before ROC|
|Seleucid era||1130/1131 AG|
|Thai solar calendar||1361–1362|
945 or 564 or −208
— to —
946 or 565 or −207
Year 819 (DCCCXIX) was a common year starting on Saturday (link will display the full calendar) of the Julian calendar.
- Spring – Emperor Louis I marries Judith of Bavaria in Aachen. She becomes his second wife and Empress of the Franks. Like many of the royal marriages of the time, Judith is selected through a bridal show.
- Ljudevit, duke of the Slavs in Lower Pannonia, raises a rebellion against the Frankish Empire. Louis I sends an army led by Cadolah of Friuli, but is defeated by the Pannonian Slavs.
- Battle of Kupa: Ljudevit defeats the Frankish forces led by Borna, a vassal of Louis I. He escapes with the help of his elite bodyguard. Ljudevit uses the momentum and invades the Duchy of Croatia.
- Nominoe, a noble Briton, is appointed by Louis I as count of Vannes in Brittany (approximate date).
- August 11 – Caliph Al-Ma'mun returns to Baghdad, securing the city's place as the capital of the Abbasid Caliphate.
- Abbasid caliph Al-Ma'mun dismisses Al-Hasan ibn Sahl, as governor of al-Iraq.
- Martianus Hiberniensis, Irish monk and calligrapher (d. 875)
- March 8 – Li Shidao, Chinese warlord
- Áed Oirdnide, king of Ailech (Ireland)
- Cadolah, duke of Friuli (Italy)
- Cairell mac Fiachnai, king of Ulaid (Ireland)
- Cheng Yi, chancellor of the Tang Dynasty
- Hisham ibn al-Kalbi, Muslim historian (b. 737)
- Liu Zongyuan, Chinese poet and official (b. 773)
- ^ Rogers, Barbara, Bernhard W. Scholz, and Nithardus. Carolingian Chronicles, Royal Frankish Annals Nithard's Histories. Ann Arbor: Univ. of Michigan, 1972. Print.