The Holy Empress Theophano was the pious wife of Emperor Leo VI the Wise, who reposed at the age of 31 around the year 894 after she dedicated her life to God as a nun. Her husband considered her to be a Saint, and as a memorial to her he built the Church of Saint Theophano next to the Church of the Holy Apostles in Constantinople, probably within a year after her death. When Theophano died, her body was likely placed in the Church of the Holy Apostles then transferred to the adjoining Church of Saint Theophano. However, certain bishops objected to Leo building a church dedicated to his wife, so Leo was forced to change the name of this church, which he then dedicated to All Saints, so as to still include his wife as one of many Saints that could be commemorated there.
It appears that when Leo was forced to make the name change, the relics of Saint Theophano were moved to the Mausoleum of Constantine. Some time after the reign of Emperor Constantine VIII Porphyrogenitos and before 1350 it was transferred to the Monastery of Saint Constantine. Patriarch Gennadios Scholarios had her relics transferred to the Church of the Holy Apostles, where there was an oratory dedicated to her inside by Emperor Constantine VII Porphyrogentios (by this time the adjoining Church of All Saints built by Emperor Leo VI for Empress Theophano had been demolished), and from there some time later it was brought to the Ecumenical Patriarchate.
Today the incorrupt and wonderworking relics of Saint Theophano rest in the Patriarchal Cathedral of Saint George at the Phanar, next to the relics of Saint Euphemia and Saint Solomone. She is commemorated on December 16th, at which time her sacred relics are moved to the center of the solea where the coffin is opened and she is venerated by the faithful.
A portion of her skull is also located at Dionysiou Monastery on the Holy Mountain.