J.R.R. Tolkien based the Elvish language Quenya largely on Finnish.
Quenya is one of the principal languages of the Elves in Tolkien’s legendarium. Tolkien developed it with detailed vocabulary, grammar, sound patterns, and historical relationships, treating it as a language with its own development rather than merely a collection of fantasy words.
Finnish strongly influenced Quenya’s phonology and grammar, while Latin and Greek also contributed inspiration. Tolkien was a philologist, so his invented languages were connected to his academic interest in how real languages change over time. Quenya is associated especially with the High Elves and with the ancient history of Valinor.
Quenya is not the same as Sindarin, another major Elvish language. Sindarin was more commonly spoken in much of Middle-earth during the events of The Lord of the Rings and drew more heavily on Welsh. Tolkien’s languages therefore represent different peoples, regions, and historical periods.