Stephen Thomas Ward (19 October 1912 – 3 August 1963) was an English osteopath and artist who was one of the central figures in the 1963 Profumo affair, a British political scandal which brought about the resignation of John Profumo, the Secretary of State for War, and contributed to the defeat of the Conservative government a year later.

In 1945, Ward began practising osteopathy in London, and rapidly became quite prominent and fashionable, with many distinguished clients. In his spare time he also studied at the Slade School and developed a talent for sketching portraits which provided a profitable sideline. His practice and his art brought considerable social success, and he made many important friends. Among these was Lord Astor, at whose country house, Cliveden, in the summer of 1961, Ward introduced Profumo to a 19-year-old showgirl and night-club model, Christine Keeler. Profumo, who was married to the actress Valerie Hobson, embarked on a brief affair with Keeler. Most of their assignations took place in Ward's home in Wimpole Mews.

Ward's friendship with the Soviet military attaché Yevgeny Ivanov, known by MI5 to be an intelligence officer, drew him to the attention of British intelligence, who sought to use him in an attempt to secure Ivanov's defection. The matter became complicated when, through Ward, Ivanov met Keeler, raising the possibility of a Profumo–Keeler–Ivanov triangle. Profumo ended his relationship with Keeler, which remained largely unsuspected until early in 1963, when the disintegration of Keeler's private life brought matters to public and press attention. Profumo denied any impropriety in a statement to the House of Commons but a few weeks later admitted his affair. He resigned from his ministerial office, parliamentary seat and membership in the Privy Council. Amid a range of rumours of widespread sex scandals in government and high society, the police began to investigate Ward. In June 1963, he was charged with prostitution offences and committed for trial.

In the trial, in July 1963, Ward was abandoned by his society friends, and exposed to the contempt and hostility of the prosecuting counsel and judge. Despite the relative paucity of evidence and the dismissal of most of the charges against him, he was convicted on two counts of living off the earnings of prostitution. Before the verdict was announced, Ward took an overdose of sleeping pills and died three days later. In 2014, the trial verdict was put under review by the Criminal Cases Review Commission, but in 2017, the commission decided not to refer the case to the Court of Appeal because the original transcript of the judge's summing up could not be found.

Born in Lemsford, Hertfordshire, Stephen Ward was the second son of Arthur Evelyn Ward, Vicar of Lemsford, and Eileen Esmée, the daughter of Thomas Mercer Cliffe Vigors. The Ward family had a military and clerical background; the Vigors family were of Anglo-Irish stock. The explorer Wilfred Thesiger was a cousin; his father, Wilfred Gilbert Thesiger, son of Frederic Thesiger, 2nd Baron Chelmsford, married Eileen's elder sister, Kathleen. Stephen's siblings were John (b. 1911), Raymond (b. 1916), and twins Bridget and Eileen (b. 1925). In 1920, the family moved to Twickenham, where Arthur Ward served as the vicar of Holy Trinity Church, then in 1922 to Torquay in Devon, when he became the vicar of St. Matthias. Arthur Ward later became a Canon of Rochester Cathedral, and, in 1934, a Prebendary of Exeter Cathedral.

Ward was educated at Canford School, in the village of Canford Magna (near the market town of Wimborne Minster) in Dorset, as a boarder, where he was punished for an assault on a fellow pupil after refusing to name the real culprit. This experience left a longstanding mark. Somewhat lazy and a regular underachiever, Ward had few realistic career choices when he left Canford in 1929.

Ward moved to London, where he worked for a few months as a carpet salesman in Houndsditch before an uncle found him a job in Hamburg as a translator in the German branch of Shell Oil. After a year, he left the Hamburg job for Paris and registered for a course at the Sorbonne, while eking out a living as a tour guide. In 1932, he returned briefly to Torquay, before moving again to London where he worked as a tea salesman.

In 1934, he was persuaded by his mother to seek qualification as an osteopath, by studying at the Kirksville College of Osteopathy and Surgery in the United States. He spent four years there, completing a course that qualified him as a general medical practitioner in the US.