William Lemen Thomas (25 September 1872 – 13 July 1921) was an Australian politician who was a member of the Legislative Assembly of Western Australia from 1911 to 1917, representing the seat of Bunbury.

In 1893, Thomas moved to Kalgoorlie, Western Australia, where he initially worked in the hospital dispensary and later had his own pharmacy.

[1] Thomas first stood for parliament at the 1908 state election, as the Labor Party's candidate for the seat of Sussex, but was defeated by Frank Wilson (a future premier).

[1] Thomas eventually entered parliament at the 1911 Bunbury by-election, which had been caused by the resignation of Sir Newton Moore (a former premier).

In June 1917, Thomas was made a minister without portfolio in the new ministry formed by Henry Lefroy, who had replaced Frank Wilson as premier.