William Young was born in Paisley, Renfrewshire, north of Glasgow, in 1843. He was articled to James Lamb and trained with William Tait of Glasgow. In the early 1860s, Young worked in Liverpool and Manchester before moving to London, where he worked for C. H. Howell, the Surrey County Surveyor.
After designing a wooden Marquee commissioned by Lord Elcho for the National Rifle Brigade, Young rose to prominence as an architect specialising in country houses, town houses, and churches. His designs include Culford Park, Suffolk, Peebles Parish Church, Scottish Borders (1874), and Gosford House, Lothian (1891).
Other notable commissions include the War Offices in Whitehall (1900-6 and completed by his son, Clyde Young), and the Glasgow City Chambers (1881-90) renowned by contemporaries for the interior decor and sculpture.