Mardi Gras in New Orleans, Louisiana is one of the most famous Carnival celebrations in the world.

The New Orleans Carnival season, with roots in the start of the Catholic season of Lent, starts on Twelfth Night (January 6). The season of parades, balls (some of them masquerade balls), and king cake parties begins on that date.

From about two weeks before, through Fat Tuesday, there is at least one major parade each day. The largest and most elaborate parades take place the last five days of the season. In the final week of Carnival many events large and small occur throughout New Orleans and surrounding communities.

The parades in New Orleans are organized by Carnival krewes. Krewe float riders toss throws to the crowds; the most common throws are strings, usually made of plastic colorful beads, doubloons (aluminium or wooden dollar-sized coins usually impressed with a krewe logo), decorated plastic throw cups, and small inexpensive toys. Major krewes follow the same parade schedule and route each year.

While many tourists center their Mardi Gras season activities on Bourbon Street and the French Quarter, none of the major Mardi Gras parades have entered the Quarter since 1972 because of its narrow streets and overhead obstructions. Instead, major parades originate in the Uptown and Mid-City districts and follow a route along St. Charles Avenue and Canal Street, on the upriver side of the French Quarter.

To New Orleanians, "Mardi Gras" refers only to the final and most elaborate day of the Carnival Season; visitors tend to refer to the entire Carnival as "Mardi Gras." Some locals have thus started to refer to the final day of Carnival as "Mardi Gras Day" to avoid confusion.