Why do Spanish people have two last names?

Spanish naming customs are distinctive in that individuals typically have two surnames, one inherited from their father and the other from their mother. This practice can be traced back to the medieval era, when it was common for individuals to be identified by their father's name followed by their mother's name.

Legally speaking, individuals in Spain are required to use both their father's and mother's surnames, although in some cases, it is possible for an individual to choose to omit one of the surnames. This practice is more common among women, who may choose to use their mother's surname as their primary or only surname.

When addressing an individual in a formal setting, it is customary to use both of their surnames, preceded by the appropriate title (Mr., Mrs., Miss, etc.). For example, if a woman's name is "María López García", she would be addressed as "Ms. López García". In less formal settings, it is common to refer to individuals by their first name only.