The Church of the Holy Apostles, also known as the Imperial Polyandrion, was a Byzantine Eastern Orthodox church in Constantinople, capital of the Eastern Roman Empire. The first structure dated to the 4th century, though future emperors would add to and improve upon it. It was second in size and importance only to the Hagia Sophia among the great churches of the capital.

Constantinople became the capital of the Roman Empire during the reign of Constantine the Great in 330. Following the collapse of the Western Roman Empire in the late 5th century, Constantinople remained the capital of the Eastern Roman Empire, the Latin Empire (1204–1261), and the Ottoman Empire (1453–1922). Following the Turkish War of Independence, the Turkish capital then moved to Ankara. Officially renamed Istanbul in 1930, the city is today the largest city in Europe, straddling the Bosporus strait and lying in both Europe and Asia, and the financial centre of Turkey.