The fictional language J.R.R. Tolkien based largely on Finnish is Quenya.
Tolkien developed Quenya as one of the major languages of the Elves in his mythology. Its sound and structure were strongly influenced by Finnish, while its vocabulary and history were shaped within Tolkien’s own invented linguistic world. Quenya is associated especially with the High Elves and is often presented as an ancient, formal, or literary language.
Quenya is not the same as Sindarin, another major Elvish language. Tolkien based Sindarin’s sound system primarily on Welsh, and the two languages have different histories inside Middle-earth. Both belong to the Elvish language family Tolkien created, but they serve different cultural and historical roles.
Tolkien was a professional philologist, and his languages were built with grammar, sound changes, and historical relationships rather than as collections of decorative words. This linguistic depth helped make Middle-earth feel like a world with its own long past.