What is the usual Spanish plural of “quinceañera”?

The usual Spanish plural of “quinceañera” is “quinceañeras.”

Spanish forms the plural by adding -s to this noun because it ends in an unstressed vowel. The ñ remains part of the spelling, so the plural is written quinceañeras rather than replacing or removing that letter.

In context, quinceañeras can mean multiple young women celebrating the tradition, or multiple celebrations when the word is being used as a shortened label for the events. English-language writing often uses the same plural form, although some writers may describe the parties as quinceañera celebrations instead.

This word should not be confused with quinceañero, a masculine noun that can refer to a male participant or, in some usage, a male counterpart celebration. Spanish gender and number endings can change the meaning, so preserving both the ñ and the final vowel is important.