The 1st Battalion, Canadian Mounted Rifles, CEF, was an infantry battalion of the Canadian Army. Raised for service during the First World War as part of the Canadian Expeditionary Force (CEF), it was formed in November 1914, in Brandon, Manitoba. Originally a mounted infantry unit named the 1st Regiment, Canadian Mounted Rifles, CEF, which was expanded, following its rerolling and dismounting as an infantry unit, by absorbing other units of the Canadian Mounted Rifles (CMR).