Marcellus of Ancyra (Greek: Μάρκελλος Άγκυρας, died c. 374) was a Bishop of Ancyra and one of the bishops present at the Council of Ancyra and the First Council of Nicaea. He was a strong opponent of Arianism, but was accused of adopting the opposite extreme of modified Sabellianism. He was condemned by a council of his enemies and expelled from his see, though he was able to return there to live quietly with a small congregation in the last years of his life. He is also said to have destroyed the temple of Zeus Belos at Apamea.