Hōon-ji, Buddhist temple in Yonezawa, Japan.

Hōon-ji is a Shingon Buzan-ha temple in Yonezawa, Yamagata Prefecture, with the mountain name Hakkai-san and Dainichi Nyorai as its principal image. It serves as the family temple of the Uesugi clan and stands on the site of the Uesugi family mausoleum, where it was moved in 1870.

Founded in 737 at the foot of Mount Hakkai in Echigo, present-day Minamiuonuma, Niigata, by imperial order of Emperor Shōmu, the temple became a prayer temple of Minamoto no Yoritomo in 1197 and later of Uesugi Kenshin, who moved it to Kasugayama. In 1601 Uesugi Kagekatsu relocated it to the second enclosure of Yonezawa Castle, and in 1870 the separation of Shinto and Buddhism brought it to its present site by the Uesugi family mausoleum.

Hōon-ji is the family temple (bodaiji) of the Uesugi clan. Its bronze Bishamonten standing statue, called the "Doroku Bishamonten" (mud-footed Bishamonten), is said to have been worshipped daily by Uesugi Kenshin and is a prefectural cultural property designated in 2022. The temple also keeps a hibutsu image of the Zenkō-ji Nyorai, said to have been brought from Shinano during the Battle of Kawanakajima; a substitute image is shown once a year.

The temple grounds are typically open during daytime hours and visitors should dress respectfully as it is a religious site. The rakan figures are housed in indoor halls and are best viewed in natural daylight.

The temple's principal image is a bronze Bishamonten standing statue known as the "Mudashi Bishamonten" (muddy-footed Bishamonten), said to have been venerated daily by Uesugi Kenshin; it was designated a prefectural cultural property on 5 April 2022. The temple also keeps a hibutsu image of the Zenkō-ji Nyorai, said to have been brought from Shinano during the Battles of Kawanakajima; a substitute image is shown once a year, while the original is never displayed.