At Disney World, you'll find lockers in all 4 theme parks AND at both of the water parks.
The lockers at most parks have gotten fancy and high-tech in recent years.
In the parks where the switch has been completed, guests paying with credit/debit card or cash will be able to rent a locker directly from a kiosk located nearby the lockers themselves.
The kiosks are really easy to use and quite self-explanatory.
If you are using a MagicBand or any other form of payment other than cash or a credit/debit card (like a gift card) OR if you are at a location that hasn't transitioned over to the new kiosks, you'll need to go to the nearest store and ask a Cast Member there for assistance. They'll be able to help you out and get you a locker rented quite quickly!
To use a kiosk you indicate the size of locker you want and then pay (with either cash or credit card). After you pay you are then allowed to select a personalized 4-digit PIN code that you will use to open your locker.
Lockers come in 3 sizes but all 3 sizes aren't available everywhere.
Standard (12.5″ x 10″ x 17″) --> $7/day
Large: (15.5″ x 13″ x 17″) --> $9/day
Extra Large/Jumbo: (17” x 22” x 26”) only available at Magic Kingdom and Epcot --> $15/day
*International Gateway - at the same location as the stroller rental area
*Front of the park - to the right of Spaceship Earth (with your back to the front of the park), near the restrooms
*On the right side as you enter the park
*To the left side directly after you enter the park, near Guest Services
*To the right after you enter the park, near Oscar's Super Services
More information on locker rental at Blizzard Beach
More information on locker rental at Typhoon Lagoon