Eustratius of Constantinople

Eustratius or Eustratios (; 582–602) was a hagiographer, theologian and priest of Hagia Sophia in Constantinople.

Eustratios was a native of Melitene. whose biography he wrote.

Eustratios also wrote a tract against belief in soul sleep entitled A Refutation of Those Who Say That the Souls of the Dead Are Not Active and Receive No Benefit from the Prayers and Sacrifices Made for Them to God. A Latin translation of this work De statu animarum post mortem was reprinted in 1841. It was written between 582 and 602, possibly in or about 593–594, when there arose in Constantinople a controversy over some miracles attributed to Euphemia.

Gregory the Great's Dialogues, composed around the same time, deal with similar themes as Eustratios' Refutation. Matthew Dal Santo hypothesises that the two men may have known each other in Constantinople.