Sir William Ewart, 1st Baronet (22 November 1817 – 1 August 1889)^[1] was an Irish linen manufacturer and Unionist politician who sat in the House of Commons from 1878 to 1889.

Ewart was the son of William Ewart of Sydenham Park County Down. He was educated at the Belfast Academy. He was a linen manufacturer and merchant and became president of the Irish Linen Trade Association. In 1859 he was mayor of Belfast and was also some time a member of the Belfast Local Marine Board. He was a magistrate for Antrim and Belfast.^[2]

Ewart was Member of Parliament (MP) for Belfast from 1878 until the constituency was divided under the Redistribution of Seats Act 1885,^[3] and then for the Northern Division of Belfast until his death,^[3] at which point Sir Edward Harland, Bt. was elected unopposed.^[4] Ewart was created a baronet on 13 September 1887, of Glenmachan House, in the parish of Holywood in the County of Down and of Glenbank, in the parish of Belfast in the County of Antrim.^[5][1]

He was one of the Directors of the XIT Ranch, located in the Texas Panhandle.

Ewart married Isabella Kelso Mathewson daughter of Lavens Mathewson of Newtownstewart, County Tyrone.^[2][6]