The Irrawaddy dolphin is patchily distributed in shallow, near-shore tropical and subtropical marine waters of the Indo-Pacific, from northeastern Australia in the south, north to the Philippines (Dolar et al. 2002) and west to northeastern India (Stacey and Leatherwood 1997; Stacey and Arnold 1999). Its marine distribution is concentrated in estuaries and semi-enclosed water bodies (i.e., bays and sounds), generally adjacent to mangrove forests. Freshwater populations occur in three river systems - the Mahakam of Indonesia, the Ayeyarwady (formerly Irrawaddy) of Myanmar (formerly Burma) and the Mekong of southern Laos, Cambodia and Viet Nam. Irrawaddy dolphins also occur in partially isolated brackish or fresh-water bodies, including Chilka Lake in India and Songkhla Lake in Thailand.

The earliest reference to dolphins in the Ayeyarwady River is from the New T’ang History (Chinese text from ‘about 800 A.D.’ as cited in Luce 1966), which mentions trade in ‘river pigs’ among the Pyu people. During surveys of the Ayeyarwady River between Rangoon [Yangon] and Bhamo, Anderson (1879) observed Irrawaddy dolphins no farther downstream than Prome [Pyay] (about 360 km from the sea) during the low-water season and Yenanyoung (about 540 km from the sea) during the high-water season. Upstream, the local Shan people reported to Anderson (1879) that dolphins were never found upriver of a point 30 m above Bhamo, where the course of the river was interrupted by rocks. They called the site Labine, or "Dolphin Point." Anderson (1879) also reported that the dolphins ascended larger tributaries, such as the Taping, Khyendwen [Chindwin] and Shuaylee [Shweli], when these were in flood. (See Figure 1 in the attached PDF for a map of the Ayeyarwady River and the locations used to describe the distribution of the dolphin).