The Shingon/Mikkō Order of Japanese Buddhism traces its origins to the Chinese C'hen-yen/Mitsung Order, which in turn traces its origin to three Indian monks who arrived in China from India in the 8th century.

In Japan however the Japanese monk Kūkai (posthumously named Kōbō Daishi) is generally regarded to be the founder of the Shingon/Mikkō Order.
The monk Kūkai was sent to the T'ang capital of China by the Heian Court to study Buddhism and Sanskrit for twenty years. After just two years, in 800 CE, his Chinese teacher Hui-ko sent him back to Japan. Arriving back in Japan earlier than expected the court in Nara was displeased and initially gave Kūkai no support.

Finally settling on Mount Kōya, Kukai founded the Japanese Shingon which is largely based upon the Mahāvairocana Sūtra (Dainichikyo), and the Vajrashekhara Sūtra.
After Kūkai's death numerous sub-groups evolved, among them the Kōyasan-ha is presently the largest, followed by the Chizan-ha and the Buzan-ha.

A Shingon Ritsu Order (employing the Vināya rules of the Sarvāstivādins) was established by Myōnin in 1602 at Kōzanji in Kyoto. Later, during the Meiji Era, by decree of the government, the remainders of the relatively small Ritsu-shū (Vināya/Disciple Order) were incorporated into Shingon-shū, leading to further sub-groupings within the order. According to a 1962 survey the Shingon-shū then had about 12,000 Temples, 23,000 Teachers and 12,000,000 members.

Today Mount Kōya with its 119 temples remains the center of the Shingon/Mikkō Order (see below).