The Battle of Pegae (Bulgarian: битка при Пиги) was fought between 11 and 18 March 921 in the outskirts of Constantinople between the forces of the Bulgarian Empire and the Byzantine Empire during the Byzantine–Bulgarian war of 913–927. The battle took place in a locality called Pegae (i.e. "the spring"), named after the nearby Church of St. Mary of the Spring. The Byzantine lines collapsed at the very first Bulgarian attack and their commanders fled the battlefield. In the subsequent rout most Byzantine soldiers were killed by the sword, drowned or were captured.