The Martyrium Pionii is an anonymous early Christian text from the 3rd century CE. It is not the work of a single author but a prose account documenting the arrest, trial, and execution of Pionius, a Christian presbyter in the city of Smyrna. The events are set during the Roman persecution under Emperor Decius around 250 CE, when citizens were required to perform public sacrifices to the gods.

The text presents Pionius as a learned figure who debates both pagans and Jews before his death. According to the narrative, he and his companions were executed by burning for refusing to renounce their faith. The account deliberately connects his martyrdom to the earlier death of Polycarp, a celebrated bishop of Smyrna, to create a continuous tradition of local Christian heroism. Scholars treat the work as a valuable example of early martyr literature, intended to strengthen and edify Christian communities. It provides details about the procedures of Roman persecution, such as the demand for sacrifice and the certificates of compliance. Modern interpretations suggest the text was important for shaping the cult of saints and constructing a shared identity for Christians facing state pressure.