The Irrawaddy dolphin Orcaella brevirostris is a euryhaline species of oceanic dolphin found in scattered subpopulations near sea coasts and in estuaries and rivers in parts of the Bay of Bengal and Southeast Asia. It closely resembles the Australian snubfin dolphin of the same genus, Orcaella , which was not described as a separate species until It has a slate blue to a slate gray color. Although found in much of the riverine and marine zones of South and Southeast Asia, the only concentrated lagoon populations are found in Chilika Lake in Odisha , India and Songkhla Lake in southern Thailand.
One of the earliest recorded descriptions of the Irrawaddy dolphin was by Sir Richard Owen in based on a specimen found in , in the harbour of Visakhapatnam on the east coast of India.
It has sometimes been listed variously in a family containing just itself and in the Monodontidae and Delphinidae. Widespread agreement now exists to list it in the family Delphinidae.
The species' name brevirostris is from the Latin meaning short-beaked. The Irrawaddy dolphin's colour is grey to dark slate blue, paler underneath, without a distinctive pattern.
The dorsal fin is small and rounded behind the middle of the back. The forehead is high and rounded; the beak is lacking. The front of its snout is blunt. The flippers are broad and rounded. The finless porpoise Neophocaena phocaenoides is similar and has no back fin; the humpback dolphin Sousa chinensis is larger, and has a longer beak and a larger dorsal fin.
