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.

The New Orleans metropolitan area, designated the New Orleans–Metairie metropolitan statistical area by the U.S. Office of Management and Budget, or simply Greater New Orleans, is a metropolitan statistical area designated by the United States Census Bureau encompassing seven Louisiana parishes—the equivalent of counties in other U.S. states—centered on the city of New Orleans. The population of Greater New Orleans was 1,271,845 in 2020, up from 1,189,166 at the 2010 United States census. Greater New Orleans is the most populous metropolitan area in Louisiana, and the 45th most populous in the United States. According to 2017 census estimates, the broader New Orleans–Metairie–Slidell combined statistical area (CSA) had a population of 1,510,562.