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 was authorized on 22 December 1915 and began recruiting in that city. After sailing to England on RMS Empress of Britain (1905) 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: Lieutenant-Colonel Archibald Woodbury McLelan. The 121st Battalion is perpetuated by The British Columbia Regiment (Duke of Connaught's Own). The perpetuation has been passed down through the following units as a result of reorganizations and amalgamations: