A sect which sprung from the Eutychians, and so called because they allowed only one will in Christ.  The appellation is derived from monos, single, and thelo, I will.  The party originated AD 630, in the attempts which the emperor Heraclius made to unite the Monophysites with the Greek church, and establish harmony through his dominions.  Heraclius had been assured that every difference might be easily adjusted, provided both parties would assent to the following proposition; namely, ‘That in Jesus Christ there was, after the union of the two natures, but one will and one operation.’  The edict was published, and at first approved by many of the eastern prelates, and even by Honorius, bishop of Rome.  In a short time, however, the doctrine of one will, which had been propounded by imperial authority, became the occasion of renewed debates and tumults, which continued during a period of fifty years.  The Roman bishops who succeeded Honorius vehemently assailed it; and Martin I, in a bull of excommunication, AD 649, consigned the Monothelites and their patrons to ‘the devil and his angels.’  At length, in the sixth general council of the church at Constantinople, AD 680, the doctrine of the Monothelites was solemnly condemned, and an anathema pronounced on all who had at any time upheld it.  This heresy subsequently found a place among the Maronites, a people inhabiting the regions of Lebanon, in Syria.  Some of them, in the twelfth century, abandoned the doctrine of one will in Christ, and were admitted, in the year 1182, into communion with the Romish church”.

From: Farrar, John, 1878, “An Ecclesiastical Dictionary, Explanatory of the History, Antiquities, Heresies, Sects, and Religious Denominations of the Christian Church”, entry “Monothelites” p. 403-404, pub. Wesleyan Conference Office, London