List of state leaders in 857

This is a list of heads of state, government leaders, and other rulers in the year 857.

Asia

• China (Tang dynasty) – Emperor Xuānzong (846–859)
• Pratihara Empire – Mihira Bhoja I (c. 836–886)
• Japan (Heian period) – Emperor Montoku (850–858)
• Korea (North South States Period)
  • Balhae –
    1. Dae Ijin (830–857)
    2. Dae Geonhwang (857–871)
  • Unified Silla –
    1. Munseong (839–857)
    2. Heonan (857–861)

Europe

• First Bulgarian Empire – Boris I, Khan of the Bulgars (852–889)
• Byzantine Empire – Michael III (842–867)
• Caucasus
  • Principality of Iberia – Bagrat I Kuropalates (830–876)
  • Principality of Kakheti – Samuel (839–861)
• Duchy of Croatia – Trpimir I (845–864)
• Kingdom of Denmark – Horik II (854–c. 866)
• England (Heptarchy) –
  • Kingdom of East Anglia – Edmund the Martyr (854–869)
  • Kingdom of Mercia – Burgred (852–874)
  • Kingdom of Northumbria – Osberht (849–862/863)
  • Kingdom of Wessex – Æthelbald (856–860)
• East Francia – Louis the German (843–876)
  • Duchy of Saxony – Liudolf, Duke of Saxony (844–866)
  • Duchy of Thuringia – Thachulf (849–873)
• West Francia – Charles the Bald (843–877)
  • County of Angoulême – Turpio (839–863)
  • Duchy of Aquitaine – Ranulf I (854–866)
  • Kingdom of Aquitaine –
    • Pepin II of Aquitaine (854–864)
    • Charles the Child (855–866)
  • County of Barcelona – Odalric (852–858)
  • Duchy of Brittany –
    1. Erispoe (851–857)
    2. Salomon (857–874)
  • Duchy of Gascony – Sans II Sancion of Gascony (836–864)
  • County of Maine – Rorgon II (853–865)
  • County of Poitiers – Ranulf I (854–866)
  • County of Toulouse – Raymond I (852–863)
  • County of Troyes – Odo I (852–858)
  • County of Urgell – Solomon (848–869)
• Ireland – Máel Sechnaill mac Máele Ruanaid, High King of Ireland (846–862)
  • Kingdom of Ailech – Áed Findliath (c. 855–879)
  • Kingdom of Connacht – Mugron mac Máel Cothaid (848–872)
  • Uí Maine –
  • Kingdom of Leinster –
  • Kingdom of Mide – Máel Sechnaill mac Máele Ruanaid (845–862)
  • Kingdom of Munster – Máel Gualae (856–859)
  • Kingdom of Osraige – Cerball mac Dúnlainge (842–888)
  • Kingdom of Ulaid –
    1. Matudán mac Muiredaig (839–857)
    2. Cathalán mac Indrechtaig, co-king (857–871)
    3. Lethlobar mac Loingsig, co-king (857–873)
• Kingdom of Italy – Louis II (855–875)
  • Principality of Benevento – Adelchis (854–878)
  • County of Capua – Lando I (843–861)
  • March of Friuli – Eberhard (846–863)
  • Duchy of Gaeta – Constantine, Hypatus of Gaeta (839–866)
  • Duchy of Naples – Sergius I (840–864)
  • Papal States – Pope Benedict III (855–858)
  • Principality of Salerno – Adhemar (853–861)
  • Duchy of Spoleto – Guy I (842–860)
  • March of Tuscany – Adalbert I (847–886)
  • Republic of Venice – Pietro Tradonico, Doge of Venice (836–864)
• Kingdom of Lotharingia – Lothair II (855–869)
• Great Moravia – Rastislav (846–870)
• Kingdom of Provence – Charles (855–863)
• Scotland
  • Kingdom of the Picts – Kenneth I (848–858)
• Principality of Serbia – Mutimir, Grand Župan (850–891)
• Spain –
  • County of Aragon – Galindo Aznárez I (844–867)
  • Kingdom of Asturias – Ordoño I (850–866)
  • Emirate of Córdoba – Muhammad I (852–886)
  • Kingdom of Pamplona – García Íñiguez (851/852–882)
• Wales –
  • Kingdom of Gwynedd – Rhodri Mawr (844–878)
  • Kingdom of Powys – Rhodri Mawr (855–878)