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.
At the 1959 general election, he was elected as Member of Parliament for Glasgow Scotstoun. He held the seat until it was abolished for the February 1974 election, when he moved to the new Glasgow Garscadden constituency. He held that seat until death in 1978.
Small never held ministerial office, but served as Parliamentary Private Secretary to the Minister of Power from 1964.