The Spanish word quinceañera describes the girl who celebrates her fifteenth birthday in this tradition. In many contexts, the same word is also used for the celebration itself, so the surrounding sentence determines the meaning.
The word is related to quince, Spanish for fifteen. The masculine form quinceañero can refer to a boy’s fifteenth-birthday celebration or celebrant in communities that use that adaptation, although quinceañera remains the much more widely recognized term.
The celebrant is often at the center of a formal ceremony, a reception, a court, and symbolic rituals. These may include a waltz, a shoe change, a last doll, or the presentation of a tiara.
Usage varies by country and family. Some people use quince años for the celebration, while others use quinceañera for both the event and the young woman. The answer here refers specifically to the celebrant, not to an English translation of the event.