Authorities say Pierre Anton was working at a local nonprofit organization as part of a summer exchange program; he was scheduled to leave the country next week.
Anton is accused of sexually assaulting the 23-year-old woman early Saturday morning on the San Lorenzo river levee.
After his arrest, police say the victim positively identified Anton as her attacker. Police also want to talk to two men who heard the woman screaming and interrupted the attack.
Authorities have contacted the French consulate about the arrest.