List of state leaders in 857

856 state leaders - Events of 857 - 858 state leaders - State leaders by year----

Asia

*Bohai/Balhae -
*#Da Yizhen/Dae I-jin, King of Bohai/Balhae (830-857)
*#Da Qianhuang/Dae Geon-hwang, King of Bohai/Balhae (857-871)
*China (Tang Dynasty) - Xuanzong, Emperor of Tang China (846-859)
*Gurjara - Mihira Bhoja I, Pratihara King of Gurjara (c. 836-886)
*Japan (Heian Period) - Emperor Montoku, emperor of Japan (850-858)
*Silla -
*#Munseong, King of Silla (839-857)
*#Heonan, King of Silla (857-861)

Europe

*Al-Andalus - Muhammad I, Emir of Cordoba (852-886)
*Asturias - Ordoño I, King of Asturias (850-866)
*Benevento - Adelchis, Prince of Benevento (854-878)
*Bulgaria - Boris I, Khan of Bulgaria (852-889)
*East Anglia¹ - Edmund, King of East Anglia (855–870)
*East Francia - Louis the German, King of East Francia (843-876)
*England - Æthelbald of Wessex, Bretwalda (856–860)
*Friesland - Rorik, King of the Danish Vikings in Friesland (850-880)
*Holy Roman Empire - Louis, II, Holy Roman Emperor (855-875)
*Ireland -
**Bard of Limerick, High King of Ireland (845–880)
**Mael Seachlainn I, High King of Ireland (845–860)
*Italy - Louis II, King of Italy (844-875)
*Lotharingia - Lothair II, King of Lotharingia (855-869)
*Mercia - Burgred, King of Mercia (852–874)
*Northumbria¹ - Osbert, King of Northumbria (849–867)
*Papal States - Benedict III, Pope (855-858)
*Provence - Charles of Provence, King of Provence (855-863)
*Scotland -Kenneth I, King of Scots and Picts (843–858)
*Strathclyde - Arthgal f Dyfnwal, King of Strathclyde (816–872)
*Venice - Pietro Tradonico, Doge of Venice (837-864)
*Wales - Rhodri "Mawr" ap Merfyn, King of Gwynedd (844–878)
*Western Francia - Charles the Bald, King of Western Francia (843-877)

Notes

#Though East Anglia, Northumbria and Mercia are traditionally perceived to have been in the heptarchy they were largely independent kingdoms until its conquest by the Danes in 869 and 867, respectively - where Mercia was conquered by Wessex in 874. All other members of the heptarchy had been conquered by Wessex and by this time had no form or king.