Sir Arthur Vicars, KCVO (27 July 1862 – 14 April 1921) was an English-born genealogist and heraldic expert who spent his adult life in Ireland. He was appointed Ulster King of Arms in 1893, but was removed from the post in 1908 following the theft of the Irish Crown Jewels in the previous year. He was killed by the IRA in 1921 during the Irish War of Independence.
Arthur Edward Vicars was born on 27 July 1862 in Leamington Spa, Warwickshire, and was the youngest child of Colonel William Henry Vicars of the 61st Regiment of Foot and his wife Jane (originally Gun-Cunninghame). This was his mother's second marriage, the first being to Pierce O'Mahony by whom she had two sons. Arthur was very attached to his Irish half-brothers and spent much time at their residences. On completing his education at Magdalen College School, Oxford and Bromsgrove School he moved permanently to Ireland.
He quickly developed an expertise in genealogical and heraldic matters and made several attempts to be employed by the Irish heraldic administration of Ulster King of Arms, even offering to work for no pay.
In 1891 he was one of the founder members of the County Kildare Archaeological Society, and remained its honorary secretary until his death.
He first attempted to find a post in the Office of Arms when in 1892 he applied unsuccessfully for the post of Athlone Pursuivant on the death of the incumbent, Bernard Louis Burke. In a letter dated 2 October 1892 Vicars's half-brother Peirce Mahony wrote that Sir Bernard Burke, Ulster King of Arms, was dying and urged him: "You should move at once." Burke died in December 1892, and Vicars was appointed to the office by Letters Patent dated 2 February 1893. In 1896 Arthur Vicars was knighted, in 1900 he was appointed Commander of the Royal Victorian Order (CVO) and in 1903 he was elevated to Knight Commander of the order (KCVO). He was also a fellow of the Society of Antiquaries and a trustee of the National Library of Ireland.