The Lam Tsuen River is a typical medium-sized Hong Kong river. It's in the central New Territories, to the west of Tai Po New Town. The river has a total length of 10 km, the headwaters being at 740m above sea level on the northern slopes of Tai Mo Shan.

The main stream of Lam Tsuen River first flows north as it plunges down the famous Ng Tung Chai waterfall group, reaches Lam Tsuen Valley and turns northeast after passing Lam Kam Road. It flows by Ma Po Mei and Fong Ma Po, and makes an abrupt southeast turn after reaching Wei Tau Tsuen. It merges with Tai Po River at Tai Po New Town, and enters Tolo Harbour at Kwong Fuk Estate.

Middle course of Lam Tsuen River, flowing though Ngai Kong

Mui Shue Hang at the lower course

The Lam Tsuen River basin is broadly rectangular, flanked by the two parallel watersheds formed by Tai Mo Shan's northern ridges and Tai To Yan. Its main stream flows through the middle of Lam Tsuen valley, while its five major tributaries pass Kwun Yam Shan (Pak Ngau Shek), Sha Ba, Tam Shui Keng, Tai Om and She Shan Tsuen.

The lower course basin includes Lin Au and Tai Po New Town. Formerly, the mouth of Lam Tsuen River was near the Fire Station at the north of Tai Po Market. The current river section to the east of Tai Wo Estate is an artificial channel constructed after land reclamation.

Lam Tsuen Valley is flanked by Tai To Yan and Tai Mo Shan