The Chao Phraya is a major river in Thailand.with its low alluvial river plain marking the mainland of the country. It runs through Bangkok, the capital of Thailand.

The Chao Phraya begins at the confluence of the Ping and Nan river at Nakhon Sawan in the Nakhon Sawan province.It then flows from north to south for 372 kilometres from the central plains to Bangkok and the Gulf of Thailand.In Chainat, the river splits into the main river course and the Tha Chin river, which then flows parallel to the main river and exits to the Gulf of Thailand about 35 kilometres (22 mi) west of Bangkok in Samut Sakhon. The cities along the Chao Phraya are Nakhon Sawan, Uthai Thani, Chainat, Singburi, Ang Thong, Ayutthaya, Pathum Thani, Nonthaburi, Bangkok and Samut Prakan, listed from north to south.
In Bangkok, the Chao Phraya is a major transportation artery for a vast network of ferries and water taxis, also known as longtails. More than 15 boat lines operate on the riverways and canals of the city