Yes, the Eurail Pass covers TGV high-speed trains, but with a significant caveat: seat reservations are mandatory. In 2026, while your pass acts as your "ticket," you must pay an additional fee (ranging from €10 to €20 for domestic French routes and more for international ones) to secure a seat. These reservations can sell out weeks in advance, especially during the peak summer and holiday seasons, as TGV trains have a limited number of seats allocated for pass holders. If those specific "pass-holder" seats are gone, you would have to buy a full-price ticket despite having a valid Eurail Pass. It's recommended to book your TGV seats through the Eurail "Rail Planner" app or the SNCF website as soon as your travel dates are confirmed.