Costumbre is the customary religion of the Tzotzil and Tzeltal Maya of highland Chiapas, Mexico, a Maya framework of calendar, ancestor obligation and mountain and earth spirits carried inside an outwardly Catholic parish structure, maintained through ritual specialists and through cargos, a system of rotating civil religious offices that anchors community life. Its best known setting, the church at San Juan Chamula, enforces its own well publicized prohibition on photography and on close description of what happens inside during ceremonies, a rule the community sets and polices itself rather than one imposed from outside, and this article follows it rather than working around it.
What is public is the shape of the practice and its history: pine boughs, candles, incense and offerings accompany prayer inside the church in a form the anthropologist Gary Gossen and others have documented as distinct from a conventional Catholic mass, built on a traditional Maya day count that predates the parish structure it now sits within. The prohibition on photography, well known to the many visitors who travel to San Juan Chamula each year, has itself become part of the practice's public identity, a boundary the community holds in public precisely by continuing to be visited and continuing to say no. Costumbre remains a living Maya religious practice today, not a historical reconstruction.