The fictional language J.R.R. Tolkien developed with strong Finnish influence is Quenya.
Quenya is one of the major Elvish languages of Tolkien’s mythology. Tolkien began developing it during the 1910s, and Finnish grammar and sound patterns strongly influenced its structure. He also drew vocabulary and ideas from other languages, including Latin and Greek, while creating a broader linguistic history for Middle-earth.
In Tolkien’s internal history, Quenya is associated especially with the High Elves and with the ancient realm of Valinor. It remains an important ceremonial and literary language in later ages, even when Sindarin is more widely spoken among Elves in Middle-earth. Names such as Eärendil and many formal phrases reflect Tolkien’s invented linguistic traditions.
Quenya is often mixed up with Sindarin because both are Elvish languages and appear in Tolkien’s writings. Sindarin was influenced more strongly by Welsh phonology and became the common Elvish language of much of Third-Age Middle-earth. Quenya is not simply a translation of Finnish; it is Tolkien’s own constructed language.