Clandeboye or Clannaboy was a kingdom of Gaelic Ireland, comprising what is now south County Antrim, north County Down, and the barony of Loughinsholin. The entity was relatively late in appearance and is associated partly with the Gaelic resurgence of the High Middle Ages. The O'Neill Clandeboy who reigned in the territory descended from Hugh Boy O'Neill, a king of Tyrone. His descendants took advantage of the demise of the Earldom of Ulster during the latter 14th century and seized vast portions of territory. Clandeboye's main seats of power were Shane's Castle and Castle Reagh.