Clementine Churchill, Baroness Spencer-Churchill (April 1, 1885 - December 12, 1977) (née Clementine Ogilvy Hozier) was the wife of Sir Winston Churchill.

Clementine was born in London to The Lady Blanche Henrietta Hozier (1852-1925), second wife of Sir Henry Montague Hozier. Clementine's paternity, however, is a subject of some debate. Lady Blanche was well known for sharing her favours and was eventually divorced as a result. She maintained that Clementine's biological father was Capt. William George "Bay" Middleton, a noted horseman. Clementine's biographer, Joan Hardwick, has surmised (due in part to Sir Henry Hozier's reputed sterility) that all Lady Blanche's "Hozier" children were actually fathered by her sister's husband, Algernon Bertram Freeman-Mitford (1837-1916, better known as a grandfather of the infamous Mitford sisters of the 1920s). Whatever her true paternity, Clementine is recorded as being the daughter of Lady Blanche and Sir Henry.

Clementine was educated first at home, and later at Berkhamsted School for Girls (now Berkhamsted Collegiate School) and at the Sorbonne in Paris.

On 2 September 1908, at St. Margaret's, Westminster, Clementine married Sir Winston Churchill. Together they had five children: Diana (11 July 1909-1963); Randolph (28 May 1911-6 June 1968); Sarah (7 October 1914-24 September 1982, who became an actress, co-starring with Fred Astaire in the film Royal Wedding); Marigold (15 November 1918-23 August 1921); and Mary (b. 15 September 1922), who has written a book on her parents.

After her marriage, during World War I, Lady Churchill organised canteens for munitions workers on behalf of the Young Men's Christian Association (YMCA) in the North East Metropolitan Area of London. During World War II she was Chairman of the Red Cross Aid to Russia Fund, the President of the Young Women's Christian Association War Time Appeal and the Chairman of Fulmer Chase Maternity Hospital for Wives of Junior Officers. The Clementine Churchill Hospital in Harrow, Middlesex, is named after her.

After the war she was awarded honorary degrees by Glasgow University and Oxford University and later, in 1976, by Bristol University.

In 1965 Lady Churchill was created a life peer as Baroness Spencer-Churchill.

Lady Spencer-Churchill died in London. Only afterwards was it discovered that she had destroyed the famous Graham Sutherland portrait of her husband because she did not like it.