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.

Geography
As of the census of 2000, there were 2,355 people, 889 households, and 642 families residing in the city. The population density was 770.6/km² (1,996.2/mi²). There were 917 housing units at an average density of 300.0/km² (777.3/mi²). The racial makeup of the city was 98.64% White, 0.04% African American, 0.42% Native American, 0.42% Asian, 0.17% from other races, and 0.30% from two or more races. Hispanic or Latino of any race were 1.15% of the population.
There were 889 households out of which 38.1% had children under the age of 18 living with them, 58.0% were married couples living together, 11.6% had a female householder with no husband present, and 27.7% were non-families. 23.5% of all households were made up of individuals and 10.0% had someone living alone who was 65 years of age or older. The average household size was 2.59 and the average family size was 3.07.
In the city the population was spread out with 28.1% under the age of 18, 8.3% from 18 to 24, 28.6% from 25 to 44, 21.9% from 45 to 64, and 13.0% who were 65 years of age or older. The median age was 36 years. For every 100 females there were 89.9 males. For every 100 females age 18 and over, there were 86.2 males.
The median income for a household in the city was $50,112, and the median income for a family was $56,410. Males had a median income of $37,868 versus $27,569 for females. The per capita income for the city was $21,729. About 2.3% of families and 3.6% of the population were below the poverty line, including 3.4% of those under age 18 and none of those age 65 or over.