British statesman, protégé of William Ewart Gladstone (Gladstone, William Ewart), who was murdered by Irish nationalists the day after his arrival in Dublin as chief secretary to the lord lieutenant of Ireland and as a goodwill emissary from England, at the height of the Irish crisis in 1882.

The second son of the 7th Duke of Devonshire, Cavendish entered Parliament in 1865. The year before he had married Mrs. Gladstone's niece, Lucy, daughter of the 4th Baron Lyttelton. Gladstone came to admire and trust Lord Frederick, especially after taking him as private secretary in 1872, and looked to him as the future leader of the parliamentary Liberal Party. Lord Frederick was financial secretary to the Treasury from 1880, and as such he was the right-hand man of Gladstone, chancellor of the Exchequer as well as prime minister.

Gladstone then asked him to undertake the thankless and dangerous office of chief secretary for Ireland. Lord Frederick crossed to Dublin on the night of May 5, 1882. The following evening he walked across Phoenix Park (Phoenix Park murders) with Thomas H. Burke, the permanent undersecretary for Ireland. Burke was attacked by a party of Irishmen armed with knives; Cavendish tried to defend him, and both were killed. Five of their assassins, members of a secret society, the Invincibles, were betrayed and hanged in 1883; several others were sentenced to long prison terms.