The Iroha (いろは) is a Japanese poem. Originally the poem was attributed to Kūkai, the founder of Shingon Buddhism, but more modern research has found the date of composition to be later in the Heian period (794–1179). The first record of its existence dates from 1079. It is famous because it is a perfect pangram, containing each character of the Japanese syllabary exactly once. Because of this, it is also used as an ordering for the syllabary, in the same way as the A, B, C, D... sequence of the Latin alphabet.

Kūkai, born Saeki no Mao, posthumously called Kōbō Daishi , was a Japanese Buddhist monk, calligrapher, and poet who founded the esoteric Shingon school of Buddhism. He travelled to China, where he studied Tangmi under the monk Huiguo. Upon returning to Japan, he founded Shingon—the Japanese branch of Vajrayana Buddhism. With the blessing of several Emperors, Kūkai was able to preach Shingon teachings and found Shingon temples. Like other influential monks, Kūkai oversaw public works and constructions. Mount Kōya was chosen by him as a holy site, and he spent his later years there until his death in 835 C.E.