William Stanley Russell Thomas (1896 – 21 March 1957) was a physician, barrister and Welsh Liberal politician who served as a Liberal National Member of Parliament.
Educated at Brecon Grammar School, Christ College, Brecon, and Queens' College, Cambridge.
He qualified as a physician and surgeon at Guy's Hospital and was Treasurer's gold medallist in medicine.
He was called to the Bar by Lincoln's Inn in 1930.
He was Liberal candidate for Ilford in the 1931 election. It was a promising seat which the Liberals had nearly gained from the Conservatives in 1929. At the 1931 elections, the Liberal party was split into three groups and Thomas remained with the official Liberals under Sir Herbert Samuel, in support of the National Government. He finished third in Ilford, just behind the Labour candidate. He remained loyal to the official Liberal party when it left the National government in 1932.
Despite his poor showing at Ilford in 1931, for the 1935 election he was selected as Liberal candidate in the promising constituency of Aberdeenshire Central where the Liberal in 1931 finished a close second behind the Conservative in a two-party contest. However, in 1935, the Labour party intervened and in a three-way contest Thomas finished third, again just behind Labour.
His next attempt to enter parliament was also in Scotland at the Ross and Cromarty by-election, 1936. In 1935, the Liberal National candidate was re-elected unopposed. When the by-election came around, a minority section of the local Liberal Association wanted a Liberal to stand and were unhappy when the majority decided to support a National Labour candidate. The Scottish Liberal Federation persuaded Thomas to stand as a Liberal candidate. However, the result was a disaster for Thomas as he finished fourth.