Archibald Kennedy IV, Earl of Cassilis, KT (4 June 1794 – 12 August 1832), was styled Lord Kennedy until 1831, and Earl of Cassilis thereafter until his death.

Archibald was the eldest son of Archibald Kennedy, 1st Marquess of Ailsa and the former Margaret Erskine.^[1] Among his younger siblings were Lady Anne Kennedy (wife of Sir David Baird, 2nd Baronet), Lady Margaret Radclyffe Livingstone Eyre, John Kennedy-Erskine (who married Lady Augusta FitzClarence, an illegitimate daughter of King William IV), and Lady Alicia Jane Kennedy (wife of Jonathan Peel, Secretary of State for War).^[2]

His father was the eldest son of Archibald Kennedy, 11th Earl of Cassilis, by Anne Watts (a daughter of John Watts and descendant of the Schuyler family, the Van Cortlandt family, and the Delancey family of British North America).^[3]

He studied at the University of Saint Andrews under the tutorage of James Ferrie, Professor of Civil History.^[4]

As the eldest son of his father, he became known by the courtesy title Lord Kennedy 1831 when his father was elevated to the marquessate of Ailsa and he was known as the Earl of Cassilis until his death (never succeeding to the marquessate).^[3]

Lord Cassilis served as a Member of Parliament for Evesham from 1830 to 1831.^[5]

On 1 May 1814, Kennedy married Eleanor Allardyce, daughter and heiress of Alexander Allardyce of Dunnottar, Kincardine. Together, they had three daughters and nine sons, including:^[3]

• Lady Hannah Eleanor Kennedy (1815–1877), who married Sir John Cathcart, 5th Baronet.^[1]
• Archibald Kennedy, 2nd Marquess of Ailsa (1816–1870), who married Julia Jephson, daughter of Sir Richard Jephson, 1st Baronet.^[1]
• Alexander Kennedy (1818–1832), who died young.^[1]
• John Kennedy (1819–1846), who died unmarried.^[1]
• Lord David Kennedy (1820–1905), who married Lady Mary Emily Boyle, daughter of Charles Boyle, 13th Viscount Dungarvan and Lady Catherine St Lawrence (daughter of the 2nd Earl of Howth).^[1]
• Lord Gilbert Kennedy (1822–1901), who married his cousin Margaret Baird, daughter of Sir David Baird, 2nd Baronet and Lady Anne Kennedy (daughter of Archibald Kennedy, 1st Marquess of Ailsa. They had two sons, and two daughters.^[1]
• Capt. Lord William Kennedy (1823–1868), who married Sarah Jane de Blois and had three children.^[1]
• Lord Nigel Kennedy (1828–1878), who married twice. Firstly Catherine May, with whom he had three children, and secondly Elizabeth Charlotte Neeld.^[1]
• Lord Adolphus Archibald Kennedy (1832–1842), who died young.^[1]

Lord Cassilis died on 12 August 1832 before succeeded to the marquisate. Upon his father's death on 8 September 1846, his eldest son, Archibald, became the 2nd Archibald Kennedy, 2nd Marquess of Ailsa.^[1] His widow died three months later.^[5]