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. The Minamoto was the most powerful and most important clan of all four great clans that dominated Japanese politics during the Heian, Kamakura, Muromachi and Edo periods in Japanese history—the other three were the Fujiwara, the Taira, and the Tachibana.