William John Davis CH (6 August 1848 – 20 October 1934) was a British trade unionist.

Born in Birmingham, Davis began working in a brass foundry. In 1869, he represented his local reform organisation at the Trades Union Congress. In 1871, he was a founder member of the Amalgamated Brassworkers Society, becoming its first general secretary.^[1]

Davis proved an effective secretary, increasing membership to 6,000 within a year. He was also active in the local Liberal Party, and in 1876 was elected to the school board, then in 1880, he became the first Liberal-Labour member of Birmingham City Council. In 1883, he stood down from the union to become a factory inspector. Under different leadership, membership of the union fell to only 2,000, and Davis agreed to return in 1889.^[1]

Davis worked with Alexander Wilkie and Robert Knight to found the General Federation of Trade Unions in 1899. From 1906 to 1910, he published The British Trades Union Congress: History and Recollections.^[1] In 1913, he served as President of the Trades Union Congress.^[2] He strongly supported the prosecution of both the Second Boer War and World War I, after which he led a short-lived movement for the Labour Party to focus solely on trade union issues.^[1]

Davis finally retired as general secretary of the Brassworkers in 1921, after which he retired to Paris.^[1]