He was educated at St Malachy's College in Belfast and was admitted to the Irish Bar in 1845. Even before being admitted to the bar, Duffy was active on the Irish land question, and in that connection in 1842 he became an ally of James Godkin. Duffy became a leading figure in Irish literary circles. He edited Ballad Poetry of Ireland (1843) and other works on Irish literature.
Gavan Duffy was one of the founders of The Nation and became its first editor; the two others were Thomas Osborne Davis, and John Blake Dillon, who would later become Young Irelanders. All three were members of Daniel O'Connell's Repeal Association. This paper, under Gavan Duffy, transformed from a literary voice into a "rebellious organisation".
As a result of The Nation's support for Repeal, Gavan Duffy, as owner, was arrested and convicted of seditious conspiracy in relation to the Monster Meeting planned for Clontarf, just outside Dublin, but was released after an appeal to the House of Lords.
In August 1850, Gavan Duffy formed the Tenant Right League to bring about reforms in the Irish land system and protect tenants' rights, and in 1852 he was elected to the House of Commons for New Ross.
In November 1852, Lord Derby's government introduced a land bill to secure to Irish tenants on eviction, in accordance with the principles of the Tenant League, compensation for improvements prospective and retrospective made by them in the land. The bill passed the House of Commons in 1853 and 1854, but in both years failed to pass the House of Lords.
In 1855 the cause of the Irish tenants, and indeed of Ireland generally, seemed to Duffy more hopeless than ever. Broken in health and spirit, he published in 1855 a farewell address to his constituency, declaring that he had resolved to retire from parliament, as it was no longer possible to accomplish the task for which he had solicited their votes.
In 1842, he married Emily McLaughlin, who died in 1845. He married Susan Hughes in 1846, with whom he had six children.
In 1856, despairing of the prospects for Irish independence, he resigned from the House of Commons and emigrated with his family to Australia. After being feted in Sydney and Melbourne, Duffy settled in the newly formed Colony of Victoria.
A public appeal was held to enable him to buy the freehold property necessary to stand for the colonial Parliament. He was immediately elected to the Legislative Assembly for Villiers and Heytesbury in the Western District in 1856. A Melbourne Punch cartoon depicted Duffy entering Parliament as a bog Irishman carrying a shillelagh atop the parliamentary benches (Punch, 4 December 1856, p. 141.
He later represented Dalhousie and then North Gippsland. With the collapse of the Victorian Government's Haines Ministry, during 1857, another Irish Catholic, John O'Shanassy, unexpectedly became Premier and Duffy his second-in-charge. Duffy was Commissioner for Public Works, President of the Board of Land and Works, and Commissioner for Crown Lands and Survey. Irish Catholics serving as Cabinet Ministers was hitherto unknown in the British Empire and the Melbourne-based Protestants "were not prepared to counternance so startling a novelty".
In 1858–59, Melbourne Punch cartoons linked Duffy and O'Shanassy with images of the French Revolution to undermine their Ministry. One famous Punch image, "Citizens John and Charles", depicted the pair as French revolutionaries holding the skull and cross bone flag of the so-called Victorian Republic. The O'Shanassy Ministry was defeated at the 1859 election and a new government formed. Like other radicals, Duffy's main priority was to unlock the colony's lands from the grip of the squatter class, but his 1862 lands bill was amended into ineffectiveness by the Legislative Council. Historian Don Garden commented that "Unfortunately Duffy's dreams were on a higher plane than his practical skills as a legislator and the morals of those opposed to him."
In 1871 Duffy led the opposition to Premier Sir James McCulloch's plan to introduce a land tax, on the grounds that it unfairly penalised small farmers. When McCulloch's government was defeated on this issue, Duffy became Premier and Chief Secretary (June 1871 to June 1872). Victoria's finances were in a poor state and he was forced to introduce a tariff bill to provide government revenue, despite his adherence to British free trade principles.
An Irish Catholic Premier was very unpopular with the Protestant majority in the colony, and Duffy was accused of favouring Catholics in government appointments, an example being the appointment of John Cashel Hoey to a position in London. In June 1872 his government was defeated in the Assembly on a confidence motion allegedly motivated by sectarianism. He was succeeded as premier by the conservative James Francis and later resigned the leadership of the liberal party in favour of Graham Berry.
When Berry became Premier in 1877 he made Duffy Speaker of the Legislative Assembly, a post he held without much enthusiasm until 1880, when he quit politics and retired to the south of France. Duffy remained interested in both the politics of his adoptive country and of Ireland. In exile in France, Duffy was an enthusiastic supporter of the Melbourne Celtic Club, which aimed to promote Irish Home Rule and Irish culture. His sons also became members of the club.
He was knighted in 1873 and made KCMG in 1877. He married for a third time in Paris in 1881, to Louise Hall, and had four more children in his 70s. One of his sons, John Gavan Duffy, was a Victorian politician between 1874 and 1904. Another son, Sir Frank Gavan Duffy, was Chief Justice of the High Court of Australia 1931–1935. His daughter, Louise, was an Irish republican present at the 1916 Easter Rising and an Irish language enthusiast who founded an Irish language school for girls in Dublin. Yet another son, Mr Justice George Gavan Duffy (born 1882), was an Irish politician and later (from 1936) a judge of the Irish High Court, becoming its President from 1946 until his death in 1951. A grandson, Charles Leonard Gavan Duffy, was a judge on the Supreme Court of Victoria, Australia.
Sir Charles Gavan Duffy died in Nice, France in 1903, aged 86.
Texts on Wikisource:My Life in Two Hemispheres (1898)