A high king is a king who holds a position of seniority over a group of other kings. Rulers who have been termed "high king" (either by their contemporaries or by modern observers) include:

• Various ancient Celtic rulers, notably the High Kings of Ireland. Some other monarchs, such as King Arthur, Uther Pendragon, and Vortigern, have been termed "High King of Britain" in some accounts.
• The ruler of the Picts.
• The ruler of Scotland.
• Some ancient Greek rulers, such as Agamemnon (see anax).
• The most powerful king of the various Etruscan city-states.

The Yang di-Pertuan Agong in Malaysia could probably be seen as a "high king", as he is selected from among nine Malay rulers (seven Sultans, a Raja, and a Great Lord) on a rotational basis. In practice, however, the term "high king" is rarely applied to the Yang di-Pertuan Agong.

The terms "maharaja" (used by some Indian rulers), "shahanshah" (used by Persian emperors), and "daewang" (used by some Korean rulers) could possibly be translated as "high king", although "great king" is perhaps more accurate.