Quenya is the fictional language J.R.R. Tolkien based largely on Finnish while developing Middle-earth.
Tolkien was a philologist with a deep interest in the structure and history of languages. Quenya, associated especially with the High Elves or Eldar, draws inspiration from Finnish as well as from other linguistic sources. Its grammar and sound patterns were developed far beyond the needs of a few names or phrases in a story.
Sindarin is another major Elvish language, but Tolkien modeled it more strongly on Welsh. Khuzdul is the language of the Dwarves, while the Black Speech was created for the servants of Sauron. Tolkien’s languages were part of the foundation of his worldbuilding, not merely decorative vocabulary added after the stories were written.