J.R.R. Tolkien based much of Quenya's sound and structure on Finnish.
Quenya is one of the major Elvish languages in Tolkien's legendarium. Tolkien admired the grammar and sound of Finnish, and Finnish influence is especially visible in Quenya's vocabulary, inflection, and overall phonological character. He did not simply copy Finnish; he transformed its inspiration into a distinct constructed language with its own history.
Tolkien also drew on other languages when creating his linguistic world. Welsh strongly influenced the sound of Sindarin, while the languages of the Germanic tradition helped shape several Mannish tongues and names.
Quenya is associated with the High Elves and functions in the stories as an ancient, formal language. It is sometimes called the Elvish equivalent of Latin, but that comparison describes its cultural role rather than its linguistic origin. Finnish is the specific major source commonly identified for its design.