The Most Reverend Cornelius Denvir D.D. (1791–1865) was an Irish Roman Catholic Prelate, mathematician, natural philosopher and former Lord Bishop of Down and Connor. He is noted for ministering in Belfast amidst growing sectarian tension, taking a moderate and non-confrontational stance, to the annoyance of his pro-Catholic followers. He was also a professor at Maynooth College as well as Down and Connor Diocesan College, and was active in the local scientific community.
Cornelius Denvir was born on August 13, 1791 in Ballywalter, County Down. He was educated at Dr. Nelsons classical school in Downpatrick, and was described by peers as an enthusiastic child with a love for sight-seeing. According one biographer, young Denvir also showed interest in the Catechism by attending local visits from the diocesan Dr. Patrick MacMullun. In September 1808, Denvir enrolled at Maynooth College, and was appointed chair of Natural Philosophy and Mathematics there in August 1813.
Denvir was ordained first as a deacon in June of the 1813, then as a priest in May 1814, performing his liturgical duties in conjunction with his academic ones. In 1826, Denvir left Maynooth College to become the Parish Priest of Downpatrick. He became a professor at the newly founded Down and Connor Diocesan College in Belfast in 1833, teaching classes in Latin, Greek and Mathematics. He continued his duties as parish priest and professor until 1835, when he was appointed 22nd Lord Bishop of Down and Connor to succeed Dr. William Crolly.