Dom Serenus Cressy, O.S.B., (ca. 1605 –10 August 1674) was an English convert and Benedictine monk, who became a noted scholar in Church history.
He was born Hugh Paulinus de Cressy at Thorpe Salvin, Yorkshire, about 1605, the son of Hugh de Cressy and Margery d'Oylie of London. Educated first at Wakefield Grammar school, when fourteen years old he went to Oxford, where he took the degree of B.A. in 1623 and that of M.A. in 1627. He attended became a fellow of Merton College, earning his Masters degree in theology the following year.
Having taken Anglican orders, after leaving Oxford he served as chaplain to Lord Thomas Wentworth, 1st Earl of Strafford, and then to Lord Lucius Cary, 3rd Viscount Falkland, whom Cressy accompanied to Ireland in 1638. During his stay in Ireland, Cressy was appointed as Dean of Leighlin, but returned to England in 1639. He received the post of canon in the collegiate chapter of Windsor, Berkshire, in 1642, but was not able to occupy the position due to the troubled times England was experiencing then.
After his patron, Lord Falkland, was killed in battle in 1643, Cressy went into the service of Lord Charles Berkeley, who later was to become the 1st Earl of Falmouth. For some time he traveled abroad as tutor to Lord Falmouth, through the countries of Roman Catholic Europe, where he was exposed to the life and thought of that faith. Upon arriving in Rome in 1646, Cressy made the decision to enter the Roman Catholic Church. George Henry Tavard believes this decision was hastened by events of the English Civil War which brought Cressy to exile in France, where a number of Anglican High-Church adherents found French Catholicism not far from their own sympathies. Cressy took exception to the Protestant emphasis on scripture alone without authoritative interpretation. At this point he traveled to Paris to take instruction from the Reverend Henry Holden, an English theologian at the Sorbonne. He then published his most noted work, the Exomologesis, wherein he explained the motives which led him to change his religion. In some ways Cressy's views on Tradition prefigure John Henry Newman's observations in his 1845 Essay on the Development of Christian Doctrine.