Sophia is a girl's name.
Sophia is widely recognized as a feminine name, originating from the Greek word "σοφία" (sophia), which translates to "wisdom." Its historical and contemporary usage overwhelmingly identifies it as a name given to girls. The association of Sophia with wisdom and intelligence further reinforces its feminine connotation. Dictionaries and naming resources consistently list Sophia as a female name.
In summary, while theoretically names can be used across genders in some cases, Sophia is, in practice, considered and used as a girl's name.