Hans Rittervon Hemmer, (26 June 1869 – 15 December 1931), son of Colonel Anthony Hemmer, was an officer in the Royal Bavarian Army and Knight Commander of the Military Order of Max Joseph.
He was born in Munich, Kingdom of Bavaria and attended school at the humanistic Gymnasium in Regensburg, then joined on 12 August 1888 the 11th Bavarian Infantry Regiment (not the same as the 11th Bavarian Infantry Division of World War I). In 1896 he was sent for 3 years training at the Bavarian war academy, followed in 1900 by two years at the Royal Bavarian Army General Staff, another and from 1909 he worked at the Prussian General Staff in Berlin. Then, from 19 September 1912 he was at the Bavarian Army General Staff.
In World War I he participated in the fighting in August 1914 at the Battle of Lorraine, and part of the Somme. On 30 November 1914 he was promoted to lieutenant colonel and took over as Head of the General Staff of the I Royal Bavarian Reserve Corps.
On 6 July 1915, he became the Chief of General Staff of South Army in Galicia under General Felix Graf von Bothmer. On the Eastern Front in 1916 he was in heavy fighting during the fighting in Galicia, the Carpathians and Sereth, today in Romania.