The 40th Infantry Division (Russian: 40-я пехотная дивизия, 40-ya Pekhotnaya Diviziya) was an infantry formation of the Russian Imperial Army. During the First World War on 13 July 1915 the 40th Infantry Division, alongside the 50th Infantry Division successfully defended the Pultusk bridgehead from German forces attempting to cross the river Narew at Pułtusk.