In a traditional quinceañera, what birthday marks the transition celebrated by the ceremony?

A traditional quinceañera celebrates a girl’s 15th birthday as a transition into young womanhood.

The word quinceañera refers both to the celebrant and, commonly, to the birthday celebration itself. The custom is especially associated with Mexico, Central America, South America, the Caribbean, and Latino communities elsewhere.

The celebration may include a religious service, a formal entrance, a court of honor, special dances, symbolic gifts, and a family reception. Customs differ substantially by country, religion, and family, so there is no single universal ceremony.

The 15th birthday is culturally significant, but it is not a legal age of adulthood in most places. That distinction is a common source of confusion: quinceañera traditions mark a social milestone rather than a uniform legal change.