Hieromartyr Mocius, patron of the founding of Constantinople.
The Holy Hieromartyr Mocius was a priest who suffered for Christ at the beginning of the fourth century, during the persecution of Diocletian. Preaching boldly against the worship of idols, he was arrested and endured many torments, and was finally beheaded at Byzantium, faithful to the end.
He was venerated in that city from early times, and St. Constantine the Great raised a great church in his honor in the new capital. His feast on May 11 coincides with the day Constantinople was dedicated, and he is remembered as one of the city's heavenly protectors.
Feast day
On the New Calendar, Mocius the Martyr is commemorated on May 11. Churches on the Old (Julian) Calendar keep the feast on May 24 of the civil calendar.
Who celebrates a name day
People with these names keep their name day on this feast:
Also commemorated on May 11

Founding of Constantinople
Saint, Εγκαίνια Κωνσταντινουπόλεως
Commemoration of the dedication of Constantinople as the New Rome by Saint Constantine the Great.
Argyrios of Epanomi
Martyr, Αργύριος ο Επανομίτης
New Martyr Argyrios of Epanomi, a young tailor hanged at Thessalonica for confessing Christ.
Olympia and Euphrosyne of Mytilene
Holy Woman, Ολυμπία και Ευφροσύνη
Venerable Martyrs Olympia and Euphrosyne, nuns of Mytilene slain by invaders.
Name days: Olympia
Dioskoros the New
Martyr, Διόσκορος ο Νέος
New Martyr Dioskoros, who suffered at Smyrna.
Name days: Dioskoros
Icon: public domain image from Wikimedia Commons.