The Church of St. Polyeuctus (Greek: Ἅγιος Πολύευκτος, Hagios Polyeuktos) was an ancient Byzantine church in Constantinople (now Istanbul, Turkey) built by the noblewoman Anicia Juliana and dedicated to Saint Polyeuctus. Intended as an assertion of Juliana's own imperial lineage, it was a lavishly decorated building, and the largest church of the city before the construction of the Hagia Sophia.