The Seiwa Genji (清和源氏) is a line of the Japanese Minamoto clan that is descended from Emperor Seiwa, which is the most successful and powerful line of the clan.

Emperor Seiwa was father of Imperial Prince Sadazumi (貞純親王 Sadazumi Shinnō) (873–916), who was in turn the father of Minamoto no Tsunemoto (源経基) (894–961), one of the founders of the Seiwa Genji, from whom most Seiwa Genji members are descended.

Many samurai families belong to this line and used "Minamoto" clan name in official records, such as the Ashikaga, Hatakeyama, Hosokawa, Imagawa, Mori, Nanbu, Nitta, Ogasawara, Ōta, Satake, Satomi, Shiba, Takeda, Toki and the Tsuchiya, among others.

The Shimazu and Tokugawa clans also claimed to belong to this line.

An asterisk indicates a monk (who would not have been allowed to retain the Minamoto name).