The Songkhla lake is the largest natural lake of Thailand, located on the Malay peninsula in the southern part of the country. Covering an area of 1,040 km² it borders the provinces of Songkhla and Phattalung.

The lake is divided into four distinct parts. The southern part opens by a 380 m wide strait to the Gulf of Thailand at the city of Songkhla, and contains brackish water of about half the salinity of the ocean. To the north the water changes to sweet water. Further north after a bottleneck of only 6km width is the Thale Luang (782.80 km²), and finally at the northern end in between a mangrove swamp the 28 km² small Thale Noi. The most striking feature is the long 75km long spit which separates the lake from the sea. Unlike most spits, it is probably formed when originally existing islands became interconnected by the silting from the lake precursor.

A small population of Irrawaddy Dolphins is found in the lake, however threatened to extinction by the overfishing and pollution of the lake.