William Mitchell-Thomson, 1st Baron Selsdon

William Lowson Mitchell-Thomson, 1st Baron Selsdon, Bt. (1877–1938) was a British politician.

William Mitchell-Thomson was elected as a Conservative Member of Parliament for North West Lanarkshire in 1906, serving until 1910. He was then MP for Glasgow, Maryhill between 1918 and 1922, then Croydon South, South London from 1923 to 1932.

In 1922, Mitchell-Thomson was Parliamentary Secretary at the Board of Trade. From 1924 until 1929, he served as Postmaster General. He was made a Privy Counsellor the same year.

In 1932, Mitchell-Thomson resigned from the House of Commons and was made 1st Baron Selsdon.

In May 1934 the British government appointed a committee, under the guidance of Lord Selsdon, to begin enquiries into the viability of setting up a public television service, with recommendations as to the conditions under which such a service could be offered. The results of the Selsdon Report were issued as a single Government White Paper in January of the following year. The BBC was to be entrusted with the development of television. Lord Selsdon was one of those to appear on the first day of BBC television broadcasts, 2 November 1936, now in his new capacity as Chairman of the Television Advisory Committee.

Lord Selsdon died in 1938.

The 2nd Lord Selsdon, Patrick , was a racing driver who was to drive the V-12 Lagonda to 4th place at Le Mans in 1939 and to share Chinetti's winning Ferrari in that race in 1949.

• Portraits of Baron Selsdon in the National Portrait Gallery, London.