Khlong Maha Sawat also known as Khlong Chaiyaphruek is a khlong (canal) in Thailand. It is a man-made waterway dug in 1859–1860 in the reign of King Rama IV. Today it is listed by the Fine Arts Department as a national heritage site. It starts from Khlong Lat Bang Kruai (Khlong Bangkok Noi) near Wat Chaiyaphrueksamala, flows along the border of Nonthaburi's Bang Kruai with Taling Chan and Thawi Watthana of suburban Bangkok, then flows through Phutthamonthon to meet the Tha Chin River at Ngio Rai Subdistrict in Nakhon Pathom's Nakhon Chai Si District. Its length is 28 km (about 17 mi).

History
Connecting Bangkok Noi Canal and the Tha Chin (Nakhon Chaisi) River, the 28 kilometre-long Maha Sawat Canal was created as a shortcut to Phra Pathom Chedi and to open up land on both banks to agriculture. In 1852, King Rama IV ordered the restoration of Phra Pathom Chedi and assigned Somdej Chao Phraya Maha Prayoonrawong and his son, Chao Phraya Thipakornwong Maha Kosathibodi (Kham Bunnag), to supervise the digging of the Chedi Bucha and Maha Sawat canals. Chinese labourers dug the canal. They began on 13 September 1859 and finished on 1 May 1860.