William Watson Small (19 October 1909 – 18 January 1978) was a Scottish Labour Party politician. Small was an engineer. He was an Ayrshire County Councillor from 1945 to 1951 and an active member of the Amalgamated Engineering Union, serving on its national committee from 1955 to 1957 and as president of the union's West Ayrshire district. Small never held ministerial office, but served as Parliamentary Private Secretary to the Minister of Power from 1964.