Hi and welcome to planDisney, Victor!
You have asked a great question because if you are like me, the earlier I can visit any of the theme parks on any given day, the better. It is so magical to experience them all first thing in the morning.
Early Theme Park Entry begins 30 minutes before the official park opening for that day for resort guests. For example, if Magic Kingdom opens to all guests at 9:00 AM, the Disney Resort Hotel Guests can enter at 8:30 AM. So the earliest a non-resort guest can enter is 9:00 AM. I recommend arriving a bit earlier and rope-drop so that when they allow you in, you can get a glimpse of a somewhat empty(ish)
Magic Kingdom Theme Park, even if it is just for a few minutes (it is worth it if you ask me).
Before you arrive, be sure to have your theme park tickets linked to your
My Disney Experience account and make your theme park reservations using the
Disney Parks Pass Reservation System.
Please let us know if you need additional assistance prior to your arrival.
Have a magical experience!
Raquel