In J.R.R. Tolkien’s legendarium, the High Elves spoke Quenya.
Quenya is one of Tolkien’s best-developed constructed languages. He based parts of its sound and structure on languages including Finnish, and he treated it as an ancient, prestigious language associated especially with the Eldar who lived in Valinor. In the stories, it remained important in names, poetry, ceremony, and historical records.
Quenya is often contrasted with Sindarin, another major Elvish language. Sindarin became the everyday language of many Elves in Middle-earth, while Quenya had a more formal or historical role there. Both languages belong to Tolkien’s larger family of invented Elvish languages.
The word “High Elves” can refer to different groups depending on the period and context, but Quenya is the standard answer for their language. Tolkien created extensive vocabulary and grammar rather than merely inventing a few decorative words.