Sir William Arthur Stanier F.R.S. (27 May 1876 - 27 September 1965) was Chief Mechanical Engineer of the London, Midland and Scottish Railway.
He was born in Swindon where his father worked for the Great Western Railway (GWR) as William Dean's Chief Clerk. He was educated at Swindon High School and also for a single year at Wycliffe College, Stonehouse, Gloucestershire. He followed his father into a career with the GWR. Between 1897 and 1900, Stanier worked as a draughtsman, before becoming Inspector of Materials in 1900. In 1904, George Churchward appointed him as Assistant to the Divisional Locomotive Superintendent in London. In 1912 He returned to Swindon to become the Assistant Works Manager. In 1920 he was promoted to the post of Works Manager.
He was head-hunted and became Chief Mechanical Engineer (CME) of the London, Midland and Scottish Railway from January 1, 1932.
He was also president of the Institution of Mechanical Engineers.
William Stanier, with the backing of Sir Josiah Stamp, Chairman of the Company, reversed the small engine policy and saved the LMS. Designs introduced by Stanier include:
- LMS Class 2P 0-4-4T (designed in the Midland Railway design office)
- LMS Class 3MT 2-6-2T
- LMS Class 4MT 2-6-4T
- LMS Class 5MT 2-6-0
- LMS Class 5MT "Black Five" 4-6-0
- LMS Class 6P "Jubilee" 4-6-0
- LMS Class 8P "Princess Coronation" 4-6-2
- LMS Class 8P "Princess Royal" 4-6-2
- LMS Class 8F 2-8-0
- LMS Turbomotive