Theodorus of Heraclea was a Christian bishop and theologian of the 4th century CE. He served as the bishop of Heraclea in Thrace, in the eastern Roman Empire. He was a prominent figure in the major theological debates of his time concerning the nature of Christ.

Theodorus belonged to the "Eusebian" party, a large group of bishops and theologians who opposed the key term of the Nicene Creed. He participated in important church councils, including the Synod of Antioch in 341 CE and the Council of Sardica in 343 CE. Later Christian historians described him as a learned and skilled interpreter of scripture, even while disagreeing with his theological conclusions.

None of Theodorus's own writings survive intact. His literary output is known only through fragments quoted by his theological opponents, such as Athanasius of Alexandria. These references show he wrote a commentary on the Gospels and theological treatises. In these works, he used scriptural interpretation to argue for a distinction between God the Father and the Son.

Modern scholars see Theodorus as a significant representative of the mainstream, non-Nicene theology that was influential in the 4th-century church. His significance lies in his role as a scriptural exegete for the Eusebian party. The preservation of his work by his critics indicates he was considered a substantive opponent. The fragments of his writing provide valuable insight into the biblical interpretation and theological debates that defined early Christianity.