Wat Ratchanaddaram (Thai: วัดราชนัดดาราม) is a Theravada Buddhist temple (wat) located at the intersection between Ratchadamnoen Klang and Mahachak Road, in Phra Nakhon district, Bangkok. Meaning Royal Niece, the temple was built to the order of King Nangklao (Rama III) for Mom Chao Ying Sommanus Wattanavadi (หม่อมเจ้าหญิงโสมนัสวัฒนาวดี) in 1846.
The temple is best known for the Loha Prasat (โลหะปราสาท), a one of a kind in structure Thailand. The pagoda is a replica of the Loha Prasat built in India. It is 36 m high and has 37 metal spires, signifying the 37 virtues toward enlightenment. In the past, Loha Prasat was hidden behind an old movie theatre named Chalerm Thai. The theatre were demolished in 1989 as a project to improve scenery along Ratchadamnoen Road.
In 2005, the temple was submitted to UNESCO for consideration as a future World Heritage Site.