The Marmara Region is a geographical region in northwestern Turkey. It is bordered by Greece and the Aegean Sea to the west, Bulgaria and the Black Sea to the north, the Black Sea Region to the east, and the Aegean Region to the south. At the center of the region is the Sea of Marmara. The largest city in the region is Istanbul. Other big cities are Bursa, İzmit, Balıkesir, Tekirdağ, Çanakkale and Edirne.
Among the seven geographical regions, the Marmara Region has the second-smallest area, but the most people. It is the most densely populated region in the country.