The Elvish language created by J.R.R. Tolkien with a strongly Finnish-inspired structure is Quenya.
Quenya is one of Tolkien’s major constructed Elvish languages. He developed its sound and grammar partly under the influence of Finnish, alongside influences from Latin and Greek. In Tolkien’s internal history, Quenya is associated especially with the High Elves and with the Elves of Valinor, giving it a formal and literary status in Middle-earth.
Tolkien created languages as part of a broader mythology, rather than inventing isolated word lists for published stories. He revised Quenya repeatedly over many decades, and surviving manuscripts show changes in vocabulary, spelling, and grammar. This makes Tolkien’s languages subjects of philological study as well as elements of fiction.
Sindarin is another major Elvish language and is more closely associated with the Grey-elves of Middle-earth. Khuzdul is the secret language of the Dwarves, while the Black Speech was devised for the servants of Mordor. These are distinct from Quenya, even though Tolkien’s linguistic world connects them historically.