Gretna is a city in Sarpy County, Nebraska, United States. The population was 2,355 at the 2000 census; the population was estimated to be 4,860 in 2005. Gretna has the fastest rate of growth of any Nebraska city since 2000. Gretna apartments for rent comparison page shows most up to date rent information on Gretna apartments and houses. Rent information is obtained from multiple rental sources but we cannot guarantee their accuracy.