Henry John May (16 July 1867 – 19 November 1939) was a British co-operative movement activist. Born in Woolwich, May left school at thirteen to work at the Royal Arsenal Co-operative Society (RACS). He completed an engineering apprenticeship at the Royal Arsenal and joined the Amalgamated Society of Engineers, but after meeting Thomas Blandford, directed his spare time back to the RACS. He joined its board and became editor of its journal, Comradeship, then in 1898 was elected to the national board of the Co-operative Union. From 1905 until 1913, he was secretary of the Union's southern region, and in 1909 became secretary of the Co-operative Congress' Parliamentary Committee.