William Regis Colbourne CBE (16 December 1895 – 19 November 1979) was an Australian political organiser and trade unionist.

He served as general secretary of the Australian Labor Party (New South Wales Branch) from 1954 to 1969.

When the party split the following year, Colbourne and the New South Wales delegation boycotted the federal conference, but unlike in Victoria remained loyal to the ALP.

He was elected federal president of the ALP in July 1961, serving a single one-year term and then becoming senior vice-president until 1971.

He died during an ALP event in Broken Hill, New South Wales, on 19 November 1979, aged 83.