Yankee Sullivan (born James Ambrose; c. 10 March 1811 – 31 May 1856), also known as Frank Murray and James Sullivan, was a bare-knuckle fighter and boxer. He claimed the American bare knuckle heavyweight champion from 1851 to 12 October 1853. When Tom Hyer vacated his title, he laid claim to it, though many modern boxing historians dispute his claim. He lost any claim to the title after losing a fight to John Morrissey.