List of state leaders in 668

Africa

China (Tang Dynasty) - Gaozong, Emperor of China (650–683)
Japan (Asuka period) - Tenji, Emperor of Japan (661–672)
Khmer Empire - Jayavarman I (657-681)
Korea (Three Kingdoms)
- Goguryeo
  - Bojang, King of Goguryeo (642–668)
  - Conquered by Tang and Silla
- Silla - Munmu, King of Silla (661–681)
Tibet - Khri-mang-slon-rtsan, Emperor of Tibet (650–677)

Bulgaria -
- Batbayan, Khan of Bulgaria (665–668)
- Asparukh of Bulgaria, Khan of Bulgaria (668–695)
Byzantine Empire -
- Constans II, Byzantine Emperor (641–668)
- Constantine IV, Byzantine Emperor (668–685)
England (Heptarchy) - Oswiu of Northumbria, Bretwalda
- Kingdom of East Anglia - Ealdwulf of East Anglia (664–713)
- Kingdom of Essex -
  - Sighere of Essex (664–683)
  - Sebbi of Essex (664–694)
- Kingdom of Kent - Ecgberht of Kent (664–673)
- Mercia - Wulfhere of Mercia, King of Mercia (658–675)
- Northumbria -
  - Bernicia - Oswiu, King of Bernicia (642–670)
  - Deira - Interregnum (664–670)
- Kingdom of Sussex - Aethelwalh (c.660-c.685)
- Wessex - Cenwalh, King of Wessex (643–674)
Frankish Empire -
- Austrasia - Childeric II, King of Austrasia (662–675)
- Neustria and Burgundy - Chlothar III, King of Neustria (655–673)
Lombard Kingdom - Grimoald I of Benevento (662–671)
Scotland
- Dál Riata - Domangart mac Domnaill, King of Dál Riata (660–673)
- Kingdom of Strathclyde -
Visigothic Kingdom - Recceswinth (649–672)
Wales -
- Kingdom of Gwynedd - Cadwaladr (655–682)
- Kingdom of Powys