Phineas Leopold May was born into a Jewish family, the son of a naturalised German father and an English mother, in Essex, England on 9 May 1906. At the age of fifteen, he took a postal course at the London School of Cartoonists and later studied part-time at the Central School of Art. He was involved in Jewish communal service from 1935 onwards and later Custodian of the Jewish Museum in London until 1991.

In 1939 Phineas May and his brother Jonas were appointed by the Central British Fund for German Jewry to create and administer the Kitchener Camp at Richborough, near Sandwich in Kent, a disused First World War army camp. 4000 transmigrant young men came to the camp waiting for permanent settlement overseas. The whole rescue was funded by the British Jewish Community with help from American Jewry. Professor Norman Bentwich negotiated the immigration technicalities with the British authorities. During the Second World War most of them volunteered to fight for the Allies. May also served in the British Army in the Second World War and produced some 400 cartoons, now in the Imperial War Museum.

Phineas May was a member of Hampstead Synagogue and was the Shul's administrator from 1960 to his retirement in 1971. He also served as a member of Ben Uri's Council from 1974–93. He published 'A Cartoon History of Anglo-Jewry' in 1980. Phineas May died in London, England in 1995.