Honmyō-ji (本妙寺) is a Buddhist temple of the Nichiren sect, Rokujōmon-ryū (六条門流), in Nishi-ku, Kumamoto, Japan.

In Honmyō-ji is the grave of Katō Kiyomasa, (1562–1611), a Japanese daimyō, builder of Kumamoto Castle and a dedicated buddhist of Nichiren Buddhism.

From the temple, a steep slope consisting of 176 stone steps called Munatsuki Gangi begins, which leads to the grave.

It is observed to console the spirit of Katō Kiyomasa, by writing the long Lotus Sutra during one night by many priests.

The temple in Osaka was moved to Kumamoto Castle in 1600 and the grave of Katō Kiyomasa, which is called Jōchibyō was built in the present site of Mount Nakao in 1611.