James Macmahon PC (Ire) (20 April 1865 – 1 May 1954) was an Irish civil servant and businessman. Macmahon was born in Belfast and raised as a Roman Catholic. He was educated at St Patrick's College, Armagh and Blackrock College in Dublin. He joined the Irish Post Office, being promoted to Assistant Secretary in 1913 and Secretary in 1916. In 1918, he became Under-Secretary for Ireland.