John Cornelius (Irish: Seán Conchobhar Ó Mathghamhna; 1557 – 4 July 1594) also called Mohun, was an Irish Catholic priest and Jesuit born in Cornwall. He is a Catholic martyr, beatified in 1929. Life John Cornelius was born John Conor O’Mahony, in 1557 of Irish parents at Bodmin, in Cornwall, on the estate of Sir John Arundell of Lanherne. O'Mahony later Latinized his middle name, taking the name John Cornelius. Sir John Arundell took an interest in the boy and sent him to Exeter College, Oxford. Cornelius went on to the seminary at Reims, and a little later, on 1 April 1580, entered the English College, Rome, to pursue theological studies. After ordination in 1583, he was sent as a missionary to England and served for nearly ten years, making Arundell's London house his base of operations. While acting as chaplain to Sir John's widow Anne, Lady Arundell, he was arrested on 24 April 1594, at Chideock Castle, by the sheriff of Dorsetshire, having been betrayed by one William Holmes, a servant whom he had reprimanded for bothering one of the maids. Cornelius was met on the way by Thomas Bosgrave, a relative of the Arundell family, who offered him his own hat, as he had been dragged out bareheaded. Thereupon Bosgrave was arrested. Two servants of the castle, John (or Terence) Carey and Patrick Salmon, natives of Dublin, shared the same fate. When they reached the sheriff's house a number of Protestant clergymen heaped abuse on the Catholic religion, but the sheriff stopped the disputation. The missionary was sent to London and brought before the Lord Treasurer, the Archbishop of Canterbury, and others, who, by threats and torture, tried to obtain the names of those who had given him shelter or assistance. He was brought back to Dorchester. Cornelius was accused of high treason, because he was a priest and had returned to England, contrary to the Jesuits, etc. Act 1584; the others were charged with felony, for having rendered assistance to one whom they knew to be a priest; but all were assured that their lives would be spared if they embraced Protestantism. While in prison, John Cornelius was admitted to membership in the Society of Jesus. Their trial took place in the main hall of what is now Chideock House Hotel and they were condemned to death on 2 July 1594 and executed in Dorchester two days