Siddeley may mean: Siddeley-Deasy, a British automobile, engine and aircraft company based in Coventry in the early 20th century Hawker Siddeley, a group of British manufacturing companies engaged in aircraft production Armstrong Siddeley, a British engineering group that operated during the first half of the 20th century John Siddeley, 1st Baron Kenilworth, a captain of the automobile industry in Britain