Born in Thessaloniki. The childless parents begged him from God. When his father, the duke of Thessaloniki, died, Emperor Maximian appointed Demetrius as duke in his father's place and especially recommended him to persecute the Christians. But, instead of persecuting Christians, Demetrius publicly confessed Christ in Thessalonica. When the emperor came to Thessaloniki, he called Demetrius and when he confessed his faith in Christ in front of him, he threw him into prison. Knowing what awaits him, he leaves all his possessions to his servant Lupo to distribute to the poor. An angel of God appeared to him in prison and strengthened him. After a few days, according to the emperor's order, the soldiers stabbed him with spears in the dungeon. As the protector of Thessaloniki, he saved this city many times. In Russia, he is considered the protector of Siberia.
Venerable Martyr Joasaph. Memorial of the great earthquake in Constantinople.