Alfred John Barnes PC (1887 – 26 November 1974) was a British Labour Co-operative politician.
Born in North Woolwich, he was the youngest child of William Barnes, a docker. Barnes lost a leg in a fairground accident at the age of 8. He was educated at the Northampton Institute and the Central School of Arts and Crafts.
Barnes worked originally as an artist in gold and silver. He was an early member of the Independent Labour Party and was heavily involved in the co-operative movement. He was chairman of the London Co-operative Society for nine years until 1923 and was a founder of the Co-operative Party. He became the Party's chairman in 1924 and served until 1945. He was also a director and President of the National Cooperative Publishing Society.
In November 1922, Barnes was elected as the Member of Parliament (MP) for East Ham South. In 1925 he was appointed a Labour Whip and served as a whip in Government, as Junior Lord of the Treasury. However, he was forced to resign in October 1930 - although his position as a director of the National Cooperative Publishing Society was unpaid, parliamentary rules dictated that a minister cannot be a director of a public company (although they could be of a private company): Barnes chose to remain on the co-op board rather than as a whip. Like many Labour MPs, he lost his seat in the 1931 general election but regained it in 1935.