The Most Reverend Cornelius Denvir D.D. (1791–1865) was an Irish Roman Catholic Prelate, mathematician, natural philosopher (physicist) and former Lord Bishop of Down and Connor.
Dr Denvir was born in Ballywalter in County Down in 1791 and was educated as a young boy in Dr Nelsons 'classical school' in Downpatrick. He entered Maynooth College in 1808 and was ordained in 1814. After doctoral studies he taught Natural Philosophy and Mathematics at Maynooth. Among his students at Maynooth was the inventor and physicist Fr. Nicholas Callan, whom he introduced to electricity and magnetism. He also taught the noted physician Sir Dominic Corrigan Bart., MD, MP, who was a student of the lay college in Maynooth at the time.
He became Parish Priest of Downpatrick in 1825. He became Professor at the New Down and Connor Diocesan College which was situated in Belfast in 1833. He took the higher classes in Latin, Greek and Mathematics but retained his duties as P.P. in Downpatrick and returned there on horseback every weekend.
He was appointed 22nd Lord Bishop of Down and Connor in 1835 to succeed Dr William Crolly who had been appointed Archbishop of Armagh. He appointed Rev. Dr Patrick Dorrian as Coadjutor Bishop of Down and Connor in 1860. Bishop Dorrian succeed him to the see in 1865 when Dr Denvir died in 1865.