Yes, in 2026, advance booking is absolutely required for Disneyland Resort in California. You cannot simply walk up to the gate and buy a ticket for immediate entry. The resort uses a dual-requirement system: you must have both a valid theme park ticket and a specific date reservation. Reservations can be made up to 120 days in advance (and sometimes up to 8 months during specific rolling release periods). While you can often find availability a day or two before your visit during slower seasons, popular dates like weekends, holidays, and summer breaks often sell out weeks or even months in advance. Magic Key passholders have an even more restricted reservation calendar that fills up very quickly. For 2026, it is strongly recommended to check the "Theme Park Reservation Availability" calendar on the Disneyland website before purchasing your tickets to ensure your preferred dates are open. If you are staying at a Disney-owned hotel, you may have access to a separate, slightly more flexible reservation pool.