For the best prices in 2026, you should book high-speed and international European trains 2 to 4 months in advance. Most major operators like SNCF (France), Renfe (Spain), and Eurostar open their booking "horizons" about 120 days out. Booking early can save you up to 70% compared to "day-of" prices, which function similarly to airline pricing. For example, a Paris-to-London Eurostar ticket might be €44 if booked 3 months ahead, but €200 on the day of travel. For regional or local trains (like those in Switzerland or Belgium), prices are usually fixed, so there is no financial benefit to booking early. However, for "Nightjet" sleeper trains or peak-season scenic routes (like the Glacier Express), you should book as soon as the window opens—sometimes up to 6 months in advance—as these limited cabins sell out almost instantly. In 2026, many rail apps now offer "Price Alerts," making it easier to track when the cheapest "Early Bird" tiers are released for your specific route.