A suppressed Benedictine monastery about nine miles north-west of Namur on the river Orneau in Belgium, founded c. 945 by St. Guibert (Wibert) and dedicated to St. Peter the Apostle and the holy martyr Exuperius. St. Guibert was assisted in the erection of the monastery and the selection of its monks by Erluin, who had resigned a canonry to become a monk. Some of Guibert's relatives impugned the legality of the monastic foundation on the plea that the monastery was built on fiscal land which had been given in fief to Guibert's ancestors and could not be alienated without imperial authority. Emperor Otto I summoned Guibert and Erluin to his court, but was so favourably impressed with the manner in which they defended their pious undertaking that on 20 September, 946, he issued an imperial diploma approving the foundation of Gemblours and granting it various privileges. Guibert appointed his friend Erluin first Abbot of Gemblours, while he himself become a monk at the monastery of Gorze near Metz. Twice he returned to the Gemblours; once in 954, when the Hungarians threatened to pillage the monastery, on which occasion he not only preserved it from injury, but also converted some Hungarians to the true Faith; and a second time in 957, when his brother-in-law Heribrand of Mawolt had seized the revenues of the monastery. He persuaded Heribrand to leave the possessions of the monastery unmolested in the future. On 23 May, 962, St. Guibert died at Gorze and his remains were brought to Gemblours. When monastic discipline was well established at Gemblours, Erluin attempted, at the suggestion of Count Regnier of Hainaut, to reform the monastery of Lobbes in 955. But on the night of 20 October, 958, three of the monks of Lobbes, who hated reform, assaulted Erluin in his cell, dragged him outside of the monastery, and inflicted on him serious bodily injuries. Erluin died at Gemblours on 10 August 986, after Pope Benedict VII had granted his monastery exemption and papal protection.
During the short reign of his successor Heriward (987-990), the monks voluntarily relinquished their right of exemption in favour of Bishop Notger of Liege, who was friendly disposed towards the monastery. Heriward was succeeded by Erluin II (990-1012), under whose weak administration monastic discipline greatly relaxed. His successor Olbert (1012-1048), a pious and learned abbot, restored discipline, built a new abbey church in 1022, organized a rich library, and by encouraging sacred and profane learning gave the first impulse to the subsequent flourishing condition of Gemblours. During the period of its greatest intellectual activity Gemblours was ruled over by Mysach (1048-1071); Thietmar (1071-1092); Liethard (1092-1115), and Anselm (1115-1136). Under Thietmar flourished the famous chronicler Sigebert (1030-1112), who in a neat Latin style wrote a chronicle of the world from 381-1111, a history of the Abbots of Gemblours, and other historical works of great value. His chronicle was continued by Abbot Anselm till 1136, and his history of the Abbots of Gemblours by the monk Gottschalk, a disciple of Sigebert. The learned prior Guerin, who was a famous teacher at the school of Gemblours, was a contemporary of Sigebert. In 1157 and again in 1185 the monastery was destroyed by fire, and though rebuilt, it began from this period to decline in importance. In 1505, under Abbot Arnold II of Solbrecg (1501-1511), it became affiliated with the Bursfeld Union (see Bursfeld, Abbey of). It was pillaged by the Calvinists in 1598, and was partly destroyed by fire in 1678 and again in 1712. It was just beginning to recover from these heavy misfortunes when in 1793 the Government suppressed it. The buildings are now used for a state agricultural college.
Toussaint, Histoire de l'abbaye de Gembloux (Namur, 1884); Berliere, Monastican Belge (Burges, 1890), I, 15-26; Idem in Revue Benedictine (Maredsous, 1887), IV, 303-315; Gallia Christiana, Ii, 554-568; Sigebert-Gottschalk, Gesta Abbatum Gemblacensium (till 1136), in P.L. CLX, 591-658; Mabillon, Vita S. Guiberti in Acta SS. O.S.B., saec. V, 299-314; Idem, Vita Olberti in Acta SS. O.S.B.., saec. VI, 596-606.