who are you in spanish

The usual way to say “who are you?” in Spanish is:

• ¿Quién eres?

If you need it more formal (to someone older, in a job setting, etc.):

• ¿Quién es usted?

For talking to more than one person:

• ¿Quiénes son? (“Who are you all?”)

All of these use quién (who) plus a form of the verb ser (to be).