The traditional Spanish word for a male celebrant of a fifteenth-birthday rite is quinceañero. It is the masculine counterpart to quinceañera and is formed from the same Spanish root referring to fifteen years.
The feminine form is much more widely recognized because the custom historically focused on girls’ transition into young womanhood. Boys and young men may also have fifteenth-birthday celebrations, but these are less standardized and may use different names or simply be described as a fiesta de quince años.
Quinceañero can also refer to a male participant in some discussions of the broader tradition, so local usage matters. The term should not be confused with padrino, which means a sponsor or godfather, or chambelán, a male attendant in a court. Those words describe roles rather than the person whose fifteenth birthday is being celebrated.