Ultimate Form is a Form in Kingdom Hearts III. It is triggered exclusively by Ultima Weapon's Formchange, it changes Sora's clothes to a design very similar to Final Form. It allows him to teleport around the battlefield and wield multiple swords in battle, overwhelming enemies with fast and powerful swipes that also possess great range.
Ultimate Form is signified by Sora's clothes adorning a silvery-white and black color scheme, similar to Final Form. Black wisplike stripes can be seen on his pant legs and three crowns on each of his sleeves. While wearing his original outfit during the Olympus episode, Sora's clothes do not change.
Toy Box Sora is not radically different than his Standard form although his sleeves lack the crowns and his pant legs lack the stripes.
Monster Sora's jacket changes to the Ultimate Form color scheme and his hair turns white.
Pirate Sora has crowns on his cuff links, three crowns instead of one on his hat, and his bandana changes from blue to white with swirl patterns. His inner shirt turns white and the insides of his coat tails have a swirl pattern like his pants in his Standard form.