The 1st "Warsaw" Mechanised Division () was a mechanized infantry formation of the Polish Land Forces that existed from 1955 until September 1, 2011. During this entire period, the division was headquartered in Legionowo. The unit stood down in 2011 as a result of reorganizations in the Polish Army. The division was formed in 1955 on the basis of the 1st Infantry Division of the Polish People's Army. This precursor division had existed since 1943 and saw service on the Eastern Front of the Second World War as a Soviet-controlled allied formation, part of the Polish Armed Forces in the East.