Thomas Bouquillon (16 May 1840 in Warneton, Belgium – 5 November 1902 in Brussels, Belgium) was a Belgian Catholic theologian. At the time of his death he was professor of moral theology in the Catholic University of America.
He was one of the most eminent theologians of his time, a man of prodigious erudition in theology, history of theology, church history, canon law, and bibliography. Bouquillon was active and influential in the organization of the Catholic Universities of Lille and Washington. He supported the views of Archbishop John Ireland and Edward McGlynn. He warned against appeals to Rome in moral matters when that substituted for grappling with the issues.
The second son among five children in a family of small landholders long established at Warneton near Ypres, he received his early education in local schools and in the College of St. Louis at Menin. His course in philosophy was made at Roeselare; in theology, at the seminary of Bruges.
Having entered the Georgian University in Rome, in 1863, he was ordained priest in 1865 and made doctor of theology in 1867. After ten years in the Bruges seminary (1867–77) and eight years in the Catholic University of Lille, France, as professor of moral theology, Bouquillon retired to the Benedictine monastery at Maredsous and devoted his energies to the preparation of the second edition of his treatise on fundamental moral theology.
In 1892 he accepted the chair of moral theology in the Catholic University at Washington, D.C., where he remained until his death in 1902.
Though never in robust health, he was a tireless student. When he entered the field of moral theology he found the science enjoying no prestige, dwindled to mere compilations of conclusions to the neglect of principles. It was out of touch, consequently, with the closely related dogmatic and advancing social sciences, and the methods employed in teaching it were far from perfect. In his whole career as professor and author he aimed to rescue moral theology from that condition and to restore to it its proper method and dignity.