A khlong (also commonly spelled klong; Thai: คลอง (Pronunciation)) commonly refers to a canal in Thailand. These canals are spawned by the Chao Phraya, the Tha Chin, the Mae Klong Rivers, and their tributaries particularly in the low-lying areas of central Thailand. The Thai word khlong is not limited to artificial canals. Many smaller rivers are referred to as "khlongs", followed by the name of the stream.
Historically, the Thai capital Bangkok was crisscrossed by khlongs, and so gained the nickname, "Venice of the East". Khlongs were used for transportation and for floating markets, but also for sewage disposal. Today, most of the khlongs of Bangkok have been filled in, although the Thonburi side of Bangkok (covering areas west of Chao Phraya River) still retains several of its larger khlongs.
Central Bangkok has the Khlong Saen Saeb, which is a route for a boat service that remains a vital public transportation function in the traffic-congested capital.
Traditional floating markets now exist mainly as tourist attractions. The best-known is the Damnoen Saduak in Ratchaburi Province.