Leonard John Barnes MC and Bar (1895 – 1977) was a British anti-colonialist writer, journalist and educationalist. Educated at St Paul's School, he was awarded the Military Cross and Bar during World War I while serving with the King's Royal Rifle Corps and then attended University College, Oxford, before travelling to South Africa to work as a farmer and journalist.
He wrote The New Boer War (1932) and Empire or Democracy (1939) on colonial and development issues.
Barnes made two significant contributions to studies of youth work in 1948, with two notable reports for the Jubilee Trust, on the nature and objectives of youth work.
Barnes was head of what is now the Department of Social Policy and Intervention, University of Oxford.