The 3rd Mounted Division was a Yeomanry Division of the British Army active during World War I. It was formed on 6 March 1915 as the 2/2nd Mounted Division, a replacement/depot formation for the 2nd Mounted Division which was being sent abroad on active service. In March 1916, it was renumbered as the 3rd Mounted Division and in July 1916 as the 1st Mounted Division. In September 1917, the division was reorganized as a cyclist formation and redesignated as The Cyclist Division.