Marrero is a census-designated place (CDP) in Jefferson Parish, Louisiana, United States. Marrero is on the south side of the Mississippi River, within the New Orleans–Metairie–Kenner metropolitan statistical area. The population was 32,382 at the 2020 U.S. census.

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.