The 199th (Duchess of Connaught's Own Irish Rangers) Battalion, CEF was a unit in the Canadian Expeditionary Force during the First World War. Based in Montreal, Quebec, the unit began recruiting during the winter of 1915/16 in that city. After sailing to England in December 1916, the battalion was absorbed into the 23rd Reserve Battalion, CEF on May 11, 1917. The 199th (Duchess of Connaught's Own Irish Rangers) Battalion, CEF had two Officer Commanding: Lieut-Col. H. J. Trihey (December 26, 1916—January 10, 1917) and Lieut-Col. J. V. O'Donahoe (January 10, 1917—April 11, 1917).