The Spanish term that can describe both the celebration and its young honoree is quinceañera.
In common usage, quinceañera refers to the girl celebrating her fifteenth birthday and also to the event organized for that milestone. Context usually makes the meaning clear. English speakers often use the word in the second sense, meaning the party or tradition, while Spanish usage can use it for the celebrant.
The related phrase quince años literally means “fifteen years.” The name therefore links the person and the celebration to the age being marked. The term is feminine because the traditional celebration centers on a girl, although families may adapt the event in different ways.
A quinceañera is not a single standardized ceremony. Some events are religious, some are secular, and some are modest family gatherings. The term identifies the cultural milestone more reliably than it identifies a fixed schedule, dress code, guest list, or set of symbols.