Jameson, William George (‘Willie’) (1851–1939), sportsman, was the younger son among two sons and three daughters of John Jameson (1804–81), JP, of St Marnock's, Malahide, Co. Dublin, high sheriff of Dublin city (1869), and Anne Jameson (née Haig), daughter of William Haig, of Seggie, Fife, member of the Scottish distilling family. William was a great-grandson of John Jameson (1740–1823), the Scottish-born patriarch of the notable family of Irish distillers. Educated at Blackheath and TCD, he was long associated with horseracing (especially steeplechasing) and yachting. A leading amateur rider, he won numerous point-to-point races, notably the Ward Union Hunt Cup on Cappucini, son of Ascetic. He owned many successful horses, including the Irish-bred gelding Come Away, which, trained and ridden by Harry Beasley (qv), won the Aintree Grand National in 1891 by a half-length in a thrilling and controversial finish against a high-quality field. The horse, winner in eight of ten starts, pulled up lame after the race and never again competed at top level.
Jameson in his youth sailed single-handed racing craft round the British and Irish coasts, then assisted on his father's trio of great yachts that won seven King's and Queen's Cups (1881–92). Sailing master and amateur helmsman of the legendary Britannia, a 221-ton, J-class cutter of revolutionary design owned by the prince of Wales (the future King Edward VII), through five seasons (1893–7) Jameson won numerous racing trophies, attracting intense popular interest to the minority sport. In the royal yacht's illustrious first season (1893) he combined with the captain, John Carter, to win thirty-three out of forty-three starts, losing the Brenton Reef Cup to the American yacht Navahoe, but retaining the Cape May Challenge Cup. In the late 1920s and 1930s his 481-ton cruising schooner, Magdalene II, was a regular and magnificent visitor at annual regattas off Dún Laoghaire.
He was a member of the Royal St George Yacht Club, Dún Laoghaire (vice-commodore (1921–39)); the Royal Yacht Squadron, Cowes; the Turf Club, the Curragh; and the Kildare St. Club, Dublin. An enthusiastic huntsman, he also enjoyed shooting and fishing. Modest and retiring, he shunned publicity and rarely spoke of his sporting exploits. He married first (1876) his first cousin, Henrietta Frances Haig (d. 1928), a celebrated Edwardian hostess, youngest daughter of John Haig, of Cameron Bridge, Fife, Scotland, and sister of Douglas, later Field Marshal Earl Haig; her widowed sister Mary Elizabeth married (1890) his widowed elder brother, John Jameson. He married secondly (1930) the painter Flora Mitchell (qv), whose family had long been linked with the Jamesons. William Jameson had no children by either of his marriages. He maintained a residence at 21 Princes Gate, London, SW; after his brother's death (1920) his principal residence was the family seat at St Marnock's, where he died on 16 November 1939.