The Dârjiu fortified church is a Unitarian fortified church in Dârjiu (Székelyderzs), Harghita County, in the Transylvania region of Romania. It was built by the Székely Hungarian community at a time when the area belonged to the Kingdom of Hungary. Initially Roman Catholic, it became Unitarian following the Reformation. The church is noted for its interior frescoes, and together with the surrounding village, forms part of the villages with fortified churches in Transylvania UNESCO World Heritage Site.

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.