Mulan (1998) was the first Disney animated film to feature a lead character of Chinese descent.
The heroine, Fa Mulan, is based on Hua Mulan, the legendary Chinese woman warrior celebrated in the Ballad of Mulan. Disney’s story places her in an imperial Chinese setting, where she takes her father’s place in the army after he is called to fight.
The wording is sometimes broadened to say that Mulan was Disney’s first animated film with an Asian heroine. That description is also accurate, but “Chinese” is the more specific answer: Mulan is a Chinese character, and the film draws heavily on Chinese history, visual design, customs, and folklore.
The character’s cultural identity is separate from the nationality of her voice performers. Ming-Na Wen supplied Mulan’s speaking voice in the English version, while Lea Salonga sang her songs; both performers are of Chinese or Southeast Asian heritage, but the question asks about the character’s descent.