Las Posadas is a nine-day Navidad (Christmas) celebration with origins in Spain. Las Posadas are now celebrated mainly in Mexico and Guatemala. Posada is the Spanish word for "lodging", or "accommodation.” It is written in the plural because the celebration spans a period of several nights.

In Mexico, the Christmas holidays begin unofficially with the saint's day of Our Lady of Guadalupe. The festivities are in full swing with the beginning of the posadas — celebrated each evening from December 16 to 24. They are, in fact, a novenario — nine days of religious observance based on the nine months that Maria carried Jesus in her womb.

The posadas re-enact Mary and Joseph's cold and difficult journey from Nazareth to Bethlehem in search of shelter or lodging.

Traditionally, a party is held each night in a neighborhood home. At dusk, guests gather outside the house with children dressed as shepherds, angels and sometimes, Mary and Joseph. An angel leads the procession, followed by Mary and Joseph or by guests carrying their images. The adults follow, carrying lighted candles.

Every home has a nativity scene and the hosts of the Posada act as the innkeepers. The neighborhood children and adults are the pilgrims (peregrinos). The "pilgrims" sing a traditional song asking for shelter, and the hosts sing a reply. All the pilgrims carry small, lit candles in their hands. Four people carry small statues of Joseph leading a donkey, on which Mary is riding.

The head of the procession will have a candle inside a paper lamp shade. At each house, the resident responds by refusing lodging until finally the weary travelers reach the designated site for the party, where Mary and Joseph are finally recognized and allowed to enter. Once the "innkeepers" let them in, the guests come into the home and kneel around the Nativity scene to pray (typically, the Rosary). The “innkeepers” offer the “peregrinos” and their guests hot cider, fried rosette cookies known as buñuelos, steaming hot tamales and other festive foods.

The party ends with a piñata in the shape of the Christmas star. Inside the piñata, there are cnadies, fruit and other goodies for the children.

The last posada, held on December 24, is followed by midnight mass, a tradition that lives on in countless Mexican towns and cities.

Many Latin-American countries continue to celebrate this holiday with very few changes to the tradition. In some places, the final location may be a church instead of a home. Individuals may actually play the various parts of Mary (María) and Joseph with the expectant mother riding a real donkey (burro), with attendants such as angels and shepherds acquired along the way, or the pilgrims may carry images of the holy personages instead. At the end of the long journey, there will be Christmas carols (villancicos).