Dasius of Durostorum (Bulgarian: Дазий Доростолски, Greek: Δάσιος ο μάρτυρας) is a Christian martyr of the early 4th century AD.

He was a Roman soldier of Legio XI Claudiana at Durostorum (modern Silistra), Moesia Inferior who was beheaded in the early 4th century after his refusal to take the part of "king" in the local Saturnalia celebrations.

The text of the Acta Dasii as it survives does not have an earlier date than the late 4th century, as Dasius is anachronistically depicted as professing the Neo-Nicene (Niceno–Constantinopolitan) creed as laid down in 381.

[citation needed] The text is unusual for a passio because it dedicates about one third of its content to a description of the Saturnalia festival celebrated by the pagan legionaries stationed in Durostorum.

On the occasion of his visit to Bulgaria in 2002, John Paul II donated the right humerus of Dasius, taken from the Ancona relics, to the church of Silistra.

Dasius was chosen by lot to act as "king" in the Saturnalia celebrations during one month, after which he would have to cut his own throat before Saturn's altar in a form of human sacrifice.

[6] Not all of Cumont's conclusions were generally accepted, and some critics tended to believe that the Saturnalia customs among legionaries at the time might indeed have involved a human sacrifice.

Parmentier believed that no actual human sacrifice would have taken place, but argued that the claim of such was genuine to the original text, in an instance of 4th-century Christian propaganda depicting pagan customs as abhorrent.

[7][8] Frazer in his Golden Bough seemingly accepts the historicity of the human sacrifice, and its late presence in Moesia as an archaism preserving a practice which had once been universal.