The 121st (Western Irish) Battalion, CEF was a unit in the Canadian Expeditionary Force during the First World War. Based in New Westminster, British Columbia, the unit began recruiting in late 1915 in that city. After sailing to England in August 1916, the battalion was absorbed into the 16th Reserve Battalion on January 10, 1917. The 121st (Western Irish) Battalion, CEF had one Officer Commanding: Lieut-Col. A. W. McLelan. The 121st Battalion is perpetuated by The British Columbia Regiment (Duke of Connaught's Own).