Khlong San Thao (Thai: คลองสันเทา, in Thai pronounced as /kʰlɔ̄ːŋ sǎn tʰāw/) is a watercourse in the provinces of Phetchabun and Phichit, Thailand, and part of the overall Chao Phraya River basin. It is a tributary of the Nan River in the lower Nan basin.
The watercourse is referred to by various local names including the Khlong Duea (Thai: คลองเดื่อ), Khlong Yai (Thai: คลองใหญ่), Khlong Wang Pong (Thai: คลองวังโป่ง), Khlong Phikun (Thai: คลองพิกุล), Khlong Lam Prada (Thai: คลองลำประดา), Khlong Daeng (Thai: คลองแดง), Khlong Thap Khlo (Thai: คลองทับคล้อ), Khlong Bang Phai (Thai: คลองบางไผ่), Khlong Thai Thung (Thai: คลองท้ายทุ่ง) and Khlong San Thao.16.15°N 126°W