The body of Ashley Olsen, an artist from Florida, was found by her boyfriend, a fellow artist, and the property's owner, on Saturday morning, Corriere reported.
Olsen's boyfriend was concerned because he hadn't heard from her for a few days, and so asked her landlord to accompany him to the apartment in the Oltrarno area to check on her.
Her body was found with bruises to the neck and scratches, Corriere reported. An autopsy will be carried out on Monday.
Police have questioned Olsen's boyfriend and friends within the expat community, but say there is no suspect yet.