Seiwa (清和天皇, Seiwa Tennō, May 10, 850 - January 7, 881) was the fifty-sixth emperor of Japan, according to the traditional order of succession, and reigned from 858 to 876.

His personal name was Prince Korehito (惟仁). He is also called Mizunoo (水尾), after

Emperor Seiwa Genealogy

Seiwa was the fourth son of Emperor Montoku. His mother was a court lady named Akirakeiko (明子), daughter of Fujiwara no Yoshifusa, who established the Fujiwara clan's rule over Heian-era Japan from then on.

Seiwa-Tennô had many children, among them prince Sadaakira (the future emperor Yōzei) and prince Sadasumi, father of Minamoto no Tsunemoto, founder of the Seiwa Genji line.

From this lineage descended the shoguns of Kamakura and Ashikaga. The Tokugawa also claimed to be descended from this lineage (because of its illustrious precedents, the title of Sei-i-Tai-Shogun had become attached to the Seiwa Genji lineage, so only genuine descendants of the Minamoto clan could claim this prestigious title).

Wives and descendants

Emperor Seiwa had 19 children, 14 sons (10 imperial princes) and 5 daughters (4 imperial princesses)

• Fujiwara no Koshi (Takaiko), born in 842, daughter of Fujiwara no Nagara, by Fujiwara no Otoharu; adopted by her uncle Yoshifusa; imperial wife in 858; imperial lady (kotai fujin) in 877; dowager empress (kotaigo) in 882; deposed in 896; died in 910; of whom he had
• first prince: Prince Sadaakira, born 868 (future emperor Yōzei)
• second prince: Prince Sadayasu, born in 870 and died in 924
• Princess Atsuko, died 930; vestal princess of Kamo from 877 to 880
• Fujiwara no Tamishi (Tamiko), died 886, daughter of Fujiwara no Yoshisuke/ Yoshimi; imperial wife (nyogo)
• Taira no Kanshi, imperial wife (nyogo)
• Princess Kashi, daughter of prince Munesada; imperial wife (nyogo); mother of :
• fourth prince: Prince Sadazumi, born in 874, died in 916; father of Minamoto no Tsunemoto (the founder of the Seiwa Genji lineage)
• Minamoto no Seishi, his half sister, daughter of emperor Montoku; imperial wife (nyogo)
• Minamoto no Sadako, died 873; imperial wife (nyogo)
• Minamoto no Kenshi (Atsuko), imperial wife (nyogo)
• Princess Chushi (Tadako), daughter of prince Tokiyasu (emperor Koko); imperial wife (nyogo)
• Fujiwara no Yoriko, died 936, daughter of Fujiwara no Mototsune; imperial wife (nyogo)
• Fujiwara no Raishi (Kazuko), daughter of Fujiwara no Mototsune; imperial wife (nyogo); mother of:
• fifth prince: Prince Sadatoki, born 874, died 930
• Minamoto no Takeko/ Izuko, died 878, daughter of Minamoto no Yoshiari; imperial wife (nyogo)
• Minamoto no Gishi (Yoshiko), daughter of Minamoto no Okimoto; imperial wife (nyogo)
• Princess Kenshi, imperial wife (nyogo)
• Princess Ryushi, imperial wife (nyogo)
• A daughter of Tachibana no Yasukage, imperial concubine (koi); mother of
• third prince: Prince Sadakata, born in 874 and died in 930
• A daughter of Fujiwara no Nakamune, imperial concubine (koi); mother of
• Prince Sadamoto, died 909
• A daughter of Fujiwara no Yoshichika; imperial concubine (koi); mother of
• Prince Sadahira, died 913
• Princess Shikiko, born in 874 and died in 906; vestal princess of Ise from 877 to 880.
• Ariwara no Fumiko, daughter of Ariwara no Yukihira; imperial concubine (koi); mother of
• sixth prince: Prince Sadakazu, born in 875 and died in 916
• Princess Kaneko, died 889
• A daughter of Fujiwara no Morofuji, imperial concubine (koi); mother of
• eighth prince: Prince Sadazane, born in 876 and died in 932
• Princess Moshi, died 901
• A daughter of Fujiwara no Naomune, imperial concubine (koi); mother of
• seventh prince: Prince Sadayori, born in 876 and died in 922
• A daughter of Saeki no Sanefusa, imperial concubine (koi); mother of
• Minamoto no Nagami
• Minamoto no Nagayori
• A daughter of Kamo no Mineo, court lady; mother of:
• Minamoto no Naganori, died 918
• Minamoto no Saishi (Noriko)
• A daughter of Ono no Takatori, lady of the court; mother of:
• Minamoto no Nagafuchi

Biography of Emperor Seiwa

Seiwa was originally placed under the care of his maternal grandfather Fujiwara no Yoshifusa, who arranged for him to replace his half-brother Prince Koretaka as crown prince.

On the death of his father in 858, he ascended the throne. Since the new emperor was only eight years old, Yoshifusa became sesshō (regent).

He thus became the first of the Fujiwara regents, who ruled the empire de facto during the rest of the Heian period.

In 876, Seiwa abdicated suddenly and entered a Buddhist monastery. His son Prince Sadaakira ascended the throne and became Emperor Yōzei. Seiwa died in 880.

Emperor Seiwa Kugyō (公卿)

• Emperor Seiwa (清和天皇), r. 858-876 -- kugyō of Seiwa-tennō 
• Sesshō, Fujiwara no Yoshifusa (藤原良房), 858-864
• Daijō-daijin, Fujiwara no Yoshifusa (藤原良房), 857-872
• Sadaijin, Minamoto no Makoto (源信), 857-868
• Sadaijin, Minamoto no Tooru (源融), 872-895
• Udaijin, Fujiwara no Yoshisuke (藤原良相), 857-867
• Udaijin, Fujiwara no Ujimune (藤原氏宗), 870-872
• Udaijin, Fujiwara no Matotsune (藤原基経), 872-880

Eras of his reign

• Tennan Era
• Jōgan Era