John Martin was born in Loughorne, near Newry on 8 December 1812, son of Samuel Martin, a gentleman farmer and linen manufacturer and Jane (Harshaw). He was educated in Newry, where he met his lifelong friend and later brother-in-law John Mitchel; and at Trinity College, Dublin, graduating in 1834. He began to study medicine but gave it up when he inherited property in Loughorne. In 1839 he traveled America and in 1841 Europe.

In 1844 Martin joined Daniel O'Connell's Repeal Association and in 1846 joined the secession of the Young Irelanders party and was expelled from the Association. With Mitchel he tried to convince Irish protestants of the benefits of an Irish parliament and when Mitchel established The United Irishman in 1848 he contributed to it. When Mitchel was arrested for treason felony Martin used Mitchel's offices to produce Irish Felon, 'a successor to the United Irishmen.' whose sole purpose was to carry on the same policy for which Mitchel had been arraigned. For this he was tried and sentenced to transportation for ten years, arriving in Van Dieman's Land in November 1849, where subsequently he was to share a cottage with Mitchel.

In 1854 Martin was pardoned on condition that he did not return to Ireland. After a spell in Paris he received a full pardon and returned to County Down in 1858 to care for his orphaned nephews and nieces. In 1864 he established the National League, which lasted only to 1867, whose aim was to gain the legislative independence of Ireland.

In 1868 he married Henrietta Mitchel, sister of John. They had no children. In 1870 Martin joined the Home Government Association for Ireland and in 1871 was elected member of parliament for Meath, holding the seat until his death. He was involved in the creation of the Irish Home Rule League, being elected its Secretary in 1874.

Following the funeral of John Mitchell, at which he caught bronchitis, his health rapidly deteriorated. As he neared his end he was taken to Dromalane House where he died, on 29 March 1975, in the same room and the same bed in which his friend Mitchel had breathed his last. He is buried in the family plot at Donaghmore. He was affectionately known as 'Honest John' Martin.

Born:	8 September 1812
Died:	29 March 1875