The fictional language J.R.R. Tolkien based largely on Finnish and associated with many Elves is Quenya.
Tolkien developed Quenya as part of his long-running project of invented languages. Its sound and structure were influenced especially by Finnish, while its vocabulary and history were created for the mythology of the Elves. In Tolkien’s internal history, Quenya was an ancient and prestigious Elvish language.
Quenya appears in names, poems, songs, and formal speech throughout Tolkien’s writings. It is particularly associated with the High Elves, including the Noldor and Vanyar. The language is not simply “Elvish” in general: Tolkien created several related Elvish languages, each with its own history.
Sindarin is the other major Elvish language readers commonly confuse with Quenya. Sindarin became the everyday Elvish language of many Elves in Middle-earth, whereas Quenya often carried a more ceremonial or learned status.