Minamoto (源) was a noble surname bestowed by the Emperors of Japan upon members of the imperial family who were excluded from the line of succession and demoted into the ranks of the nobility since 814.

[1][2][3] Several noble lines were bestowed the surname, the most notable of which was the Seiwa Genji, whose descendants established the Kamakura and Ashikaga shogunates following the Heian era.

[4][5] In the late Heian period, Minamoto rivalry with the Taira culminated in the Genpei War (1180–1185 AD).

The name "Genpei" comes from alternate readings of the kanji "Minamoto" (源 Gen) and "Taira" (平 Hei).

The Emperors of Japan bestowed noble surnames upon members of the imperial family who were excluded from the line of succession and demoted into the ranks of the nobility.

Thereafter the Fujiwara frequently called upon the Minamoto to restore order in the capital, Heian-Kyō (modern Kyōto).

[9] The Seiwa Genji's fortunes declined in the Hōgen Rebellion (1156), when the Taira executed most of the line, including Minamoto no Tameyoshi.

[9]: 256–258  Taira no Kiyomori seized power in Kyoto by forging an alliance with the retired emperors Go-Shirakawa and Toba and infiltrating the kuge.

The bestowing of the Minamoto name on a (theretofore-)prince or his descendants excluded them from the royal class altogether, thereby operating as a reduction in legal and social rank even for ō-princes not previously in the line of succession.

The Minamoto is the ancestor and parent clan of many notable descendant clans, some of which are Ashikaga, Tokugawa, Matsudaira, Nitta, Takeda, Shimazu, Sasaki, Akamatsu, Kitabatake, Tada, Ota, Toki, Yamana, Satomi, Hosokawa, Satake, Yamamoto, Hemi, Ogasawara, Yasuda, Takenouchi, Hiraga, Imagawa, Miyake, etc.

Among his sons, Makoto, Tokiwa, and Tōru took the position of Minister of the Left (sadaijin); they were among the most powerful in the Imperial Court in the early Heian period.

This theory is not widely accepted as fact, but as Yōzei was deposed for reprehensible behaviour, there would have been a compelling motive to claim descent from more auspicious origins if it were the case.

The great-grandson of his firstborn Prince Koretada, Kōshō, was the ancestor of a line of busshi, from which various styles of Buddhist sculpture emerged.

Though they are included among the listing of 21 Genji lineages, no concrete record of the names of his descendants made Minamoto is known to survive.

They became the dōjō Shirakawa family, which headed the Jingi-kan for centuries, responsible for the centralised aspects of Shinto.

Minamoto no Yoritomo's vassal Tashiro Nobutsuna, who appears in the Tale of the Heike, was allegedly Arihito's grandson (according to the Genpei Jōsuiki).

As part of the succession dispute that led to the opening hostilities of the Genpei War, he was declassed (renamed "Minamoto no Mochimitsu") and exiled.

Koreyasu-ō was installed as a puppet shōgun (the seventh of the Kamakura shogunate) at a young age, and was renamed "Minamoto no Koreyasu" a few years later.