The common English translation of Misa de Acción de Gracias at a quinceañera is “Thanksgiving Mass.”
The Spanish phrase literally identifies a Catholic Mass offered in thanksgiving. In a quinceañera context, the family gives thanks for the celebrant's life and asks for blessings and guidance. The service may be held in a church before the reception and can include participation by the celebrant, her parents, and members of her court.
This translation describes the purpose of the service, not a separate sacrament. A quinceañera Mass is neither a wedding nor a first Communion. The celebrant may already have received other sacraments, and the exact liturgy depends on the parish and local practice.
Many quinceañeras do not include a Mass. Families may choose a secular ceremony or a service from another Christian tradition, while some simply hold the reception. The phrase is therefore useful for identifying a common Catholic component, not a universal requirement.