General Sir John Grenfell Maxwell, GCB, KCMG, CVO, DSO, PC (Ire) (11 July 1859 – 21 February 1929) was a British Army officer and colonial governor. He served in the Mahdist War in the Sudan, the Second Boer War, and in the First World War, but he is best known for ordering the execution of the leaders of the 1916 Easter Rising in Ireland. He retired in 1922.