Lansowne (sometimes erroneously spelled "Landsdowne" or confused with Lansdale) is a borough in Delaware County, Pennsylvania, United States. It is essentially a residential suburb of Philadelphia. Population in 1900, 2,630; in 1910, 4,066; and in 1940, 10, 837. The population was 11,044 at the 2000 census. Lansdowne is located 5 miles (8 km) southwest of Philadelphia.