Ryūgū-ji, Buddhist temple in Fukuoka, Japan.

Ryūgū-ji is a Jōdo-shū Chinzei-ha temple in Reisenmachi, Fukuoka, with the mountain name Reisenzan and a main image of Shō Kannon. It was rebuilt on its present site in 1600 by Hon'yō Rikaku; the grounds include a main hall and a hall called Ukimi-dō, named for the original seaside temple that was flooded at high tide.

Founded by Tani Ajō Shōnin at an unknown date, the temple first stood by the shore of Sode-no-minato and was called Ukimi-dō because high tides flooded its grounds. In 1222 a mermaid appeared in Hakata Bay; it was buried here and the temple renamed Ryūgū-ji. In 1480 the linked-verse master Sōgi lodged here and composed the Hakata Hyakuin. In 1600 Hon'yo Rikaku re-established it on its present site.

The temple's name changed to Ryūgū-ji in 1222, when a mermaid said to have appeared in Hakata Bay was buried within the grounds. The mountain name Reisenzan is linked either to the old name of Hakata Bay, Reisen-tsu, or to Reisen no Chūnagon, the court envoy sent over the mermaid affair. In 1480 the linked-verse master Sōgi stayed here and held a renga gathering; the verses, known as the Hakata Hyakuin, survive.

Ryūgū-ji stands in Reisenmachi, a short walk from the Kushida Shrine area of central Hakata. The temple was rebuilt on its present site in 1600 by Hon'yō Rikaku, so the grounds are compact and the main hall, the hall of the founding monk and the graves are seen on foot in a single visit. Look for the temple name on the gate before entering.

The temple's name changed to Ryūgū-ji in 1222, the first year of the Jōō era, after a mermaid appeared in Hakata Bay and was buried within the grounds. The mountain name Reisenzan may come from Reisen-no-Nakagon, the imperial envoy sent over the mermaid affair.