Entry, Exit and Visa RequirementsYour passport must be valid for at least three months beyond the period of stay. Review our U.S. Travelers in Europe page. You will need proof of sufficient funds and a return plane ticket. For additional information about visas for the Schengen area, see the Schengen Visa page.
People Also Ask
When entering the Schengen area as a non-EEA citizen, you do not need proof of onward travel, but proof of means of subsistence ... for the return to your country of origin or transit to a third country into which you are certain to be admitted (Schengen Borders Code, Article 5).
What is this? So while you can technically travel on a one-way ticket, they also need some kind of official return ticket confirmation showing that you are leaving the country eventually. They won't necessarily care where that ticket goes, just as long as it's out of their country.
Like many other countries, France does not require that you have proof of booked plane tickets. However, you must make sure to let the immigration officers know that you will be leaving the country and do not intend to stay for an identified period.
Although there is no requirement to have a return flight from a legal standpoint, be aware that airlines do have their own policies and do their own checks when you check-in, and might require to see some proof that you are allowed to enter as a tourist when going with a one-way flight.
In general, it can be more convenient to book a round-trip flight for a trip with specific start and end dates, but other considerations, such as cancellation policies and pricing, could make booking one-ways more appealing in some cases. And everything works differently for flights booked with miles.