The Irrawaddy (newer spelling Ayeyarwaddy) is a river that flows through the centre of Myanmar (formerly "Burma").

It is Myanmar's most important commercial waterway. Its total drainage area is about 158,700 square miles (411,000 square km). It is about 1,350 miles (2,170 km) long.

It starts in the southern Himalaya, dissects the land from north to south and empties through a nine armed delta into the Indian Ocean. In colonial times, before railways and car roads the river was known as the "Road to Mandalay".

Its name is believed to derive from the Sanskrit term "airavati", meaning "elephant river".

The Irrawaddy gives its name to a dolphin, the Irrawaddy Dolphin Orcaella brevistosus, which is found in the river. Though sometimes called the Irrawaddy River Dolphin, it is not a true river dolphin, since it is also found at sea.