Samuel George Montague Nathan (20 January 1895 – 16 July 1937) was a British volunteer in the International Brigades in Spain.
He initially commanded the British Company of the otherwise French Marseillaise Battalion but was appointed battalion commander in early 1937 following the execution of his predecessor (Major Gaston Delasalle) for espionage.He later became Chief of Staff of the XV International Brigade and was killed on 16 July 1937 at the Battle of Brunete.
Even though he had been turned down for Communist Party membership — either because of his "sexual orientation" or because of his unwillingness to "pretend great political enthusiasm" - Comintern observers admired him for his "cool arrogance under fire".