The son of a Protestant landowner, he attached himself to the Home Rule movement of Isaac Butt and was elected to the British Parliament in 1875. He quickly developed an obstructionist policy in Parliament, where his filibusters gave the Irish contingent a prominence far beyond its numbers. Although these tactics lost him the approval of Butt, they brought him the support of the militant Fenian movement.
Joining the Fenians in their agitation against the Irish land laws, Parnell became president of the National Land League (see Irish Land Question) in 1879. He encouraged the use of the boycott as a means of bringing pressure on the landlords and their agents, but the agitation also produced much violence, and the harsh Coercion Bill of 1881 was passed (over Parnell's opposition) to check it.
In 1881, Parnell started United Ireland, a paper in support of the Land League, edited by William O'Brien. Arrested for his activities and put in Kilmainham jail, Parnell directed O'Brien to compose a manifesto against rent payment. Parnell's popularity increased, and he came to be referred to as the "uncrowned king of Ireland." He was released (1882) by the so-called Kilmainham treaty, by which the government agreed to settle the question of arrears in land rent if Parnell would help check violence against landlords.
The Phoenix Park murders of 1882 shocked Parnell as much as they did the English, but the Irish leader opposed the coercive Crimes Act that followed and was therefore charged with encouraging terrorism. Nonetheless, he retained the confidence of his followers both in Ireland and in America, where the fact that he was a grandson of the American naval hero Charles Stewart added to his appeal.
In 1885 the Liberals' threat to renew the Crimes Act of 1882 led Parnell to throw the Irish vote to the Tories and thus bring down the government of William Gladstone. It was, however, an uncomfortable alliance, and in 1886 Parnell swung back to the Liberals, who returned to power. Gladstone then introduced in Parliament the first Home Rule Bill (1886), but the Liberal party split on the issue, and Gladstone's government fell again. In 1887, the London Times printed a series of hostile articles called "Parnellism and Crime," ending with a facsimile letter, purporting to carry Parnell's signature and apologizing for his denunciation of the Phoenix Park murders. A special commission found (1889) that the letter had been forged; and, although some of Parnell's activities were censured, he and his associates were exonerated.