Jefferson Parish is a parish in the U.S. state of Louisiana. As of the 2020 census, the population was 440,781. Its parish seat is Gretna, its largest community is Metairie, and its largest incorporated city is Kenner. Jefferson Parish is included in the Greater New Orleans area.

Gretna is the second-largest city in, and parish seat of, Jefferson Parish in the U.S. state of Louisiana. Gretna lies on the west bank of the Mississippi River, just east and across the river from uptown New Orleans. It is part of the New Orleans–Metairie–Kenner metropolitan statistical area. The population was 17,814 at the 2020 U.S. census.