What city outside the U.S. hosts the world's largest Mardi Gras celebration?

Rio de Janeiro, Brazil, hosts the world’s largest and most famous Carnival celebration outside the United States.

Rio Carnival takes place each year before Lent and combines enormous samba-school parades, neighborhood street parties, musical blocos, elaborate costumes, floats, and open-air performances. The formal parades are staged in the Sambadrome, where samba schools compete with themed presentations involving music, choreography, design, and storytelling.

The celebration’s roots include Portuguese colonial customs such as Entrudo, a street festival brought to Brazil in the 16th and 17th centuries. Samba became central to Rio’s Carnival during the early 20th century, shaped especially by Afro-Brazilian communities and musicians. Samba schools later developed into major neighborhood organizations that prepare throughout the year.

Strictly speaking, Rio celebrates Carnival rather than New Orleans-style Mardi Gras; both are pre-Lenten traditions. That distinction sometimes causes confusion, but Rio is the canonical answer when trivia refers to the world’s largest Carnival celebration.