You generally cannot travel to France on the Eurostar without a valid passport, as both the United Kingdom and France maintain strict border controls and are not part of a common "no-passport" travel zone for non-EU citizens. For British and international travelers, a physical passport is a mandatory requirement for check-in and immigration clearance at St. Pancras International or other Eurostar hubs. While EU citizens can sometimes use a national ID card for travel within the Schengen Area, post-Brexit rules have made the physical passport the primary requirement for almost all travelers crossing the English Channel. There are extremely rare exceptions for "Collective Passports" for certain youth groups, but for the average traveler, the "no passport, no travel" rule is absolute. Even with the new digital gates and the upcoming Entry-Exit System (EES) in 2026, the underlying requirement is a biometric passport that can be scanned to verify your identity and legal right to enter the French Republic.