Antoine de Guiscard (1658 – 17 March 1711), also known as the Marquis de Guiscard or the Abbé de la Bourlie, was a French refugee, spy and double agent who attempted to assassinate Robert Harley, a leading British statesman, on 8 March 1711 by stabbing him with a penknife during a Privy Council meeting at Whitehall. His motive is not entirely clear, although he was undoubtedly a double agent who acted as a spy for both French and British governments, and was on the point of being charged with treason by the British authorities. Personal malice against Harley, who was responsible for having Guiscard's English pension cut in half, may also have been a motive.