Sir John William O'Sullivan (c.1700 - c.1760) was an Irish professional soldier. He spent most of his career in the service of France, but is perhaps best known for his involvement in the Jacobite rising of 1745, an attempt to regain the British throne for the exiled House of Stuart. During the Rising he acted as adjutant general and quartermaster general of the Jacobite army and had a major influence on the campaign. Although many secondary works give his surname as "O'Sullivan", he used the form "Sullivan" in his own correspondence.