Demetrius of Thessaloniki

Saint Demetrius of Thessaloniki
12th-century mosaic depicting St Demetrios, from the Golden-Roofed Monastery in Kiev
Great-Martyr, Myrrh-streamer
Born	270 Sirmium, Roman Empire (now Serbia)
Died	304 (aged 33–34) Sirmium, Roman Empire (now Serbia)
Venerated in	Eastern Orthodox Church Oriental Orthodoxy Roman Catholic
Major shrine	Hagios Demetrios, Thessaloniki
Feast	26 October (Orthodox Churches) 9 April (Roman Catholic Church)
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)

Saint Demetrios of Thessaloniki (Greek: Άγιος Δημήτριος της Θεσσαλονίκης) is a 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. His feast day is 26 October for Eastern Orthodox Christians following the Gregorian calendar and 8 November for those following the Julian calendar. In the Roman Catholic church he is most commonly called "Demetrios of Sermium" and his memorial falls on 8 October.

The spelling "Demetrius" is a romanization of the ancient Greek pronunciation; the Byzantine and Modern Greek pronunciation is romanized as Dimitrios or Demetrios. See Demetrios for more on the etymology of the name.

In Russian, he is called Димитрий Солунский ([dimitri solunski] 'Dimitri of Saloniki') and was a patron saint of the Rurik dynasty from the late 11th century on. Izyaslav I of Kiev (whose Christian name was Dimitry) founded the first East Slavic monastery dedicated to this saint. The name Dimitry is in common use.

The Bulgarian Orthodox Church reveres St. Demetrios on 26 October as Димитровден (Dimitrovden).

The Romanian Orthodox Church revers St. Demetrios on 26 October as Sf. Dumitru.