List of state leaders in 842

Asia

• Bohai/Balhae - Da Yizhen/Dae I-jin , King of Bohai/Balhae (830-857)
• China (Tang Dynasty) - Wuzong, Emperor of Tang China (840-846)
• Gurjara - Mihira Bhoja I , Pratihara King of Gurjara (c. 836-886)
• Japan (Heian Period) - Nimmyo, Emperor of Japan (833-850)
• Silla - Munseong , King of Silla (839-857)

Europe

• Dalriada¹ -
  1. Alpin II, King of Dalriada (839–842)
  2. Eoganan II , King of Dalriada (842)
  3. Kenneth I, King of Dalriada (842–858)
• East Anglia² - Æthelweard , King of East Anglia (839–855)
• England - Æthelwulf of Wessex, Bretwalda (839–856)
• Mercia - Beorhtwulf, King of Mercia (840–852)
• Northumbria² - Æthelred II , King of Northumbria (841–844)
• Ireland -
  • Nial Caille , High King of Ireland (832–844)
  • Turgesius of Norway , High King of Ireland (832–845)
• Picts¹ -
  1. Uurad , King of the Picts (839–842)
  2. Brude VI , King of the Picts (842–842)
  3. Kenneth , King of the Picts (842–843)
• Strathclyde - Arthgal f Dyfnwal , King of Strathclyde (816–872)
• Wales - Merfyn Frych ap Gwriad , King of Gwynedd (825–844)

Notes

1. In this year Kenneth became king of both Dalriada and the Pictish kingdom a year later he would merge them to form Alba, retrospectively known as Scotland. His role became known as "King of Scots and Picts".
2. 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.