The Sea of Marmara (Turkish: Marmara Denizi, Modern Greek: Μαρμαρα̃ Θάλασσα or Προποντίδα) (also known as the Sea of Marmora or the Marmara Sea) is an inland sea that connects the Black Sea to the Aegean Sea, thus separating the Asian part of Turkey from its European part. The Bosporus connects it to the Black Sea and the Dardanelles to the Aegean. It has area of 11,350 km².
There are two major island groups known as the Prince's and Marmara islands. The latter group is rich in sources of marble and gives the sea its name (marmaros is the Greek word for marble).
Propontis (Προποντίς, -ίδος < pro 'before' + pontos 'Black Sea') was the ancient Greek name for the sea.