Las Posadas is a nine-day celebration with origins in Spain, now celebrated chiefly in Mexico, Guatemala and parts of the Southwestern United States, beginning December 16th and ending December 24th, on evenings (about 8 or 10 PM).

Posada is Spanish for "lodging", or "accommodation"; it is said in plural because it is celebrated more than one day in that period. The nine day novena represents the nine months of pregnancy.

The procession has been a tradition in Mexico for 400 years. While its roots are in Catholicism, even Protestant Latinos follow the tradition. It may have been started in 1538 by Friar San Ignació de Loyola or Friar Pedro de Gant in Mexico. It may have been started by early friars who combined Spanish Catholicism with the December Aztec celebration of the birth of Huitzilopochtli.

Typically, each family in a neighborhood will schedule a night for the Posada to be held at their home, starting on the 16th of December and finishing on the 24th. Every home has a nativity scene and the hosts of the Posada act as the innkeepers. The neighborhood children and adults are the pilgrims (los peregrinos), who have to request lodging by going house to house singing a traditional song about the pilgrims. All the pilgrims carry small lit candles in their hands, and four people carry statuettes of Joseph leading a donkey, on which Mary is riding.