A Brazilian police document says an unidentified woman has accused Neymar of raping her in Paris last month.
The document obtained by The Associated Press says the incident took place on May 15 at 8.20pm (local time) in a hotel.
The woman went to police on Friday in Sao Paulo.
Neymar's representatives have not replied to a request for comment. He is in Brazil preparing for the Copa America starting next week.
The woman says she and the Brazil star met in France after exchanging Instagram messages.
She told police a representative of the Paris Saint-Germain player named Gallo allegedly bought her tickets to Paris and booked her a hotel room.
She said Neymar arrived apparently drunk at 8pm and had forceful sex with her.