Castle Peak, Mountain summit in Tuen Mun, New Territories, Hong Kong.

Castle Peak, also called Pui To Shan, is a 583-metre granite peak in western Tuen Mun, Hong Kong. Its summit holds a digital television transmitter and a former British military radar relay station. The upper slopes are steep and rocky, with much of the granite exposed; the Castle Peak Hinterland to the west is a military firing range. The Tsing Shan Trail starts beside the monastery at the eastern foot.

The peak appears in records under several names: Yeung Hang Shan, then Tuen Mun Shan, after the Tang dynasty (618–907) garrison posted there to defend the coast against pirates. In 969 the Southern Han ruler Liu Chang sealed it as Sui Ying Shan and had a stele erected, which no longer survives. From 428 it was also called Pui To Shan, after the monk Pui To, who is said to have crossed the sea in his wooden bowl and landed here, where the Tsing Shan monastery was later founded.

The peak's name Pui To Shan recalls the monk Pui To, said since 428 to have crossed the sea in his wooden bowl and landed here; the Tsing Shan Monastery traces its founding to him. Taoists built the Tsing Wan Kwun temple on the site under the Daoguang emperor (1820–1850), and a Buddhist monastery followed in 1918. A gateway arch on the path was erected in 1929 under Governor Cecil Clementi.

The hike begins at Tsing Shan Tsuen Light Rail Station and takes approximately two hours to reach the summit, with clear markers along the route. Sturdy footwear is recommended, and visitors should prepare for changing weather conditions at higher elevations.

The summit carries a digital television transmitter serving Tuen Mun, Tin Shui Wai, Hung Shui Kiu, Tung Chung, the airport and parts of Yuen Long, with a radar relay station left by the British garrison nearby. The peak is grouped with Kau Keng Shan and Sharp Peak as Hong Kong's "three sharp peaks" for its steep terrain.