Three Fathoms Cove, Coastal inlet in Tai Po District, Hong Kong.

Three Fathoms Cove, also called Kei Ling Ha Hoi, is a sea inlet in Tai Po District surrounded by Shap Sze Heung, Yung Shue O, Wong Tei Tung and Sham Chung. Its eastern shore forms part of Sai Kung West Country Park, and the islands of Sam Pui Chau and Wu Chau lie within the cove. It opens north to Tolo Harbour and the Tolo Channel.

The name Kei Ling Ha Hoi refers to Ma On Shan: "Kei Ling" means that mountain, so the cove is "the sea below Ma On Shan". Its east shore forms part of Sai Kung West Country Park, and in 1994 the 1 km Tseng Tau Coast facing the cove, covering 4.3 hectares, was designated a Site of Special Scientific Interest.

The name Kei Ling Ha Hoi means "sea below Ma On Shan", since 企嶺 refers to that mountain. Villages along the shore include Tseng Tau, Nga Yiu Tau, Sai Keng, Kei Ling Ha, Yung Shue O and Sham Chung. Offshore of Yung Shue O lies one of Hong Kong's 26 designated marine fish culture zones.

The cove has no road access; it is reached on foot or by boat. The 1 km Tseng Tau Coast, a 4.3-hectare Site of Special Scientific Interest since 1994, faces the cove north of Tseng Tau village. Most of the east shore lies within Sai Kung West Country Park.

The name "Kei Ling Ha" refers to Ma On Shan: 企嶺下海 means "the sea below Ma On Shan". The cove holds two small islands, Sam Pui Chau (三杯酒, "three cups of wine") and Wu Chau (烏洲). Most of its east shore lies within Sai Kung West Country Park.