The Danube Delta (Romanian: Delta Dunăriipronounced [ˈdelta ˈdunərij] ( listen); Ukrainian: Дельта Дунаю, Del'ta Dunaju) is the second largest river deltain Europe, after Volga Delta, and is the best preserved on the continent.^[1] The greater part of the DanubeDelta lies in Romania (Tulcea County), while its northern part, on the left bank of the Chilia arm, is situated in Ukraine (Odessa Oblast). The approximate surface area is 4,152 km² (1,603 sq mi), and of that, 3,446 km² (1,331 sq mi) are in Romania. With the lagoons of Razim-Sinoe (1,015 km² (392 sq mi) with 865 km² (334 sq mi) water surface), located south of the main delta, the total area of the Danube Delta reaches 5,165 km² (1,994 sq mi). The Razelm - Sinoe lagoon complex is geologically and ecologically related to the delta proper and their combined territory is part of the World Heritage Sites.

The Danube branches into three main distributaries into the delta, Chilia, Sulina, and Sfântul Gheorghe(Saint George). The last two branches form the Tulcea channel, which continues as a single body for several kilometers after the separation from the Chilia. At the mouths of each channel gradual formation of new land takes place, as the delta continues to expand.