The Unitarian Church of Transylvania, also known as the Hungarian Unitarian Church, is a Nontrinitarian Christian denomination of the Unitarian tradition, based in the city of Cluj, Transylvania, Romania. Founded in 1568 in the Eastern Hungarian Kingdom by the Unitarian preacher and theologian Ferenc Dávid, it is the oldest continuing Unitarian denomination in the world. It has a majority-Hungarian following, and is one of the 18 religious denominations given official recognition by the Government of Romania.

Nontrinitarianism is a form of Christianity that rejects the mainstream Christian theology of the Trinity—the belief that God is three distinct hypostases or persons who are coeternal, coequal, and indivisibly united in one being, or essence. Certain religious groups that emerged during the Protestant Reformation have historically been known as antitrinitarian.