J.R.R. Tolkien based Quenya heavily on Finnish.
Quenya is one of Tolkien’s best-developed constructed languages and is associated especially with the High Elves. Tolkien admired the structure and sound of Finnish, and Finnish influence is particularly visible in Quenya’s grammar and vocabulary. He also drew on other languages, including Latin and Greek, while creating the language’s historical development.
Quenya was not simply copied from Finnish. Tolkien designed it as part of a larger family of Elvish languages, giving it its own history, sound changes, vocabulary, and relationship to languages such as Sindarin. In the mythology, Quenya is linked to the Elves of Valinor and remains a language of lore and ceremony in Middle-earth.
Sindarin is another major Elvish language, but Tolkien associated its sound and development more strongly with Welsh. Adûnaic belongs to the Men of Númenor, while Khuzdul is the language of the Dwarves.