The Polysynodial System, Polysynodial Regime (Spanish: régimen polisinodial) or System of Councils was the way of organization of the composite monarchy ruled by the Catholic Monarchs and the Spanish Habsburgs, which entrusted the central administration in a group of collegiate bodies (councils) already existing or created ex novo.[1] Most of the councils were formed by lawyers trained in academic study of Roman law.[2] After its creation in 1521 (and 1526 revamp), the Council of State, chaired by the monarch and formed by the high nobility and clergy, became the supreme body of the monarchy.[3] The polysynodial system met its demise in the early 18th century in the wake of the promulgation of the Nueva Planta decrees by the incoming Bourbon dynasty, which organized a system underpinned by Secretaries of State.