Fukō-ji, Buddhist temple in Bungoōno, Japan

Fukō-ji is a Shingon temple of the Kōyasan branch in the Asochi-chō Kamiozuka district of Bungoono, Ōita Prefecture. Its main image is Dainichi Nyorai, and its grounds hold the Fukō-ji Magaibutsu, a cliff-carved Buddhist relief designated an Ōita Prefectural Historic Site. The temple is also known as Ajisai-dera for its hydrangea plantings.

According to tradition, the temple was founded by Nichira, a 6th-century figure from Kyushu who served a Baekje king; the Bungo Kokushi records that he founded seven temples in Bungo and carved a cliff image at each, and the Fukō-ji cliff Buddha is one of them. It was damaged and declined during the 1586 Toyo-Satsu war, then gained the patronage of the Nakagawa lords of Oka Castle in the Edo period because it stood on the castle's demon gate, and received donated temple lands. It was formerly called Fukuoka-zan Chikushi-o-ji; in 1662 the third Oka lord Nakagawa Hisakiyo changed the name because Chikushi-o sounded like chikushō (beast).

The temple is known as Ajisai-dera, the hydrangea temple, for the flowers that draw visitors to its grounds. Its name was changed in 1662 by Nakagawa Hisakiyo, third lord of the Oka domain, because the old name Tsukushio could be heard as chikushō, "beast".

Fukō-ji stands in the Kamiozuka district of Asaji-chō, Bungoono, Ōita Prefecture, and is known as the Hydrangea Temple for its seasonal flowers. The temple belongs to the Kōyasan Shingon school and its main image is Dainichi Nyorai. Visitors should note that the grounds are a temple site, not a hiking trail.

The temple's former name, Fukō-san Chikushi-o-ji, was changed in 1662 by Nakagawa Hisakiyo, third lord of the Oka domain, because Chikushi-o sounded like chikushō, a word for beast. The Oka lords patronized the temple as it stood on the demon gate of Oka Castle.