Wat Hong Rattanaram Ratchaworawihan, often referred to simply as Wat Hong Rattanaram, is a historic Buddhist temple in Bangkok, Thailand, located on the banks of Khlong Bangkok Yai. The temple was founded during the late Ayutthaya period by a wealthy Chinese benefactor named Hong, whose name gave the temple various historical names, such as Wat Chao Sua Hong or Wat Chao Khrua Hong.
After the fall of Ayutthaya in 1767, King Taksin moved the capital to Thonburi and built his palace, Wang Derm, nearby. Wat Hong became an important place of worship and religious learning under his royal patronage. During the reign of King Nangklao (Rama III), the temple underwent extensive restoration.  
A prominent feature of the temple is the main Buddha statue called "Phra Saen," a bronze statue in the Lan Xang style, originally enshrined in Chiang Taeng (now Steung Treng, Cambodia). It was later transferred to this temple by King Mongkut (Rama IV) along with the Emerald Buddha. Phra Saen is considered a very sacred Buddha statue, and many worshippers make offerings to it, such as sticky rice, fermented fish (pla ra), and boiled eggs. 
The temple's architecture is remarkable, with intricately designed door and window frames and carved doors. The murals in the ordination hall (ubosot) depict the Mahanipata Jataka, the ten great birth stories of the Buddha.  
Another notable feature is the sacred pool, in which King Taksin is believed to have bathed before his military campaigns. It is believed that the water from this pond is holy and brings blessings to those who bathe or drink it.