Archelaus, born circa 250, died after 278, was a Christian preacher and bishop whose legacy is preserved through his authorship of The Acts of the Disputation with the Heresiarch Manes, a key early Christian text defending orthodoxy against Manichaeism. Likely born in Mesopotamia, possibly near Carchar (Kashkar), he emerged as bishop in a region rife with religious diversity under Persian rule. Little is known of his early life, but his role as a defender of the faith crystallized around 278, when he debated Manes, the Persian founder of Manichaeism, in a public disputation hosted by Marcellus, a pious nobleman, in Carchar. Archelaus’ preaching, as depicted in the text, was sharp and polemical, dismantling Manes’ dualistic doctrines with scriptural arguments before judges like Manippus and Aegialeus. The Acts, written in Syriac and later translated into Greek and Latin, portrays Archelaus as a steadfast apologist, though some scholars debate its historicity, suggesting it may be a literary construct rather than a verbatim record. His ministry focused on protecting his flock from heresy during a time of Christian persecution under Shapur I, blending pastoral care with intellectual rigor. Beyond the disputation, no firm details of his later life or death survive, though he likely continued leading his diocese into the late 3rd century.