Saint Demetrius (or Demetrios) of Thessalonica (Greek: Ἅγιος Δημήτριος τῆς Θεσσαλονίκης, Hágios Dēmḗtrios tēs Thessaloníkēs), also known as the Holy Great-Martyr Demetrius the Myroblyte (meaning 'the Myrrh-Gusher' or 'Myrrh-Streamer'; 3rd century – 306), was a Greek Christian martyr of the early 4th century AD.

During the Middle Ages, he came to be revered as one of the most important Orthodox military saints, often paired with Saint George of Lydda. His feast day is 26 October for Eastern Orthodox Christians, which falls on 8 November [NS, "new style"] for those following the old calendar. In the Roman Catholic Church he is most commonly called "Demetrius of Sermium" and his memorial is 9 April in the 2004 Roman Martyrology and 8 October in the martryology of the Extraordinary Form. (Full article...)
Attributes: depicted wearing the armour of a Roman soldier, usually carrying a spear, often seated on a red horse
Patronage: Thessaloniki, Siberia, Sremska Mitrovica, Kosovska Mitrovica; soldiers; Crusades (in Roman Catholic tradition); agriculture, peasants and shepherds (in the Greek countryside during Middle Ages)