Agatainukai (no) Michiyo (県犬養 三千代) (655? – February 4, 733), or Tachibana no Michiyo (橘 三千代), was a court lady of early Nara period and mother of Empress Kōmyō. She served in the courts of emperor Temmu and emperor Shomu.
In 679, around 15 years old, Michiyo became a Myōbu. On November 708, her clan was given the honorary surname "Tachibana Sukune" by Empress Genmei. In 721 she became a Buddhist nun for a brief period to pray for the health of Empress Genmei.
The Tachibana clan (橘氏, Tachibana-uji, Tachibana-shi) was one of the four most powerful court nobility (kizoku or kuge) families in Japan's Nara and early Heian periods—the other three were the Minamoto, the Fujiwara, and the Taira. Members of the Tachibana family often held high court posts within the Daijō-kan (Ministry of State), most frequently Sadaijin (Minister of the Left). Like the other major families at court, they also constantly sought to increase and secure their power by marrying into the imperial family. However, as the Minamoto clan and the Fujiwara clan gained power over the course of the 9th and 10th centuries, the Tachibana were eclipsed and eventually became scattered across the country. Though serving in high government posts outside the capital, they were thus denied the degree of power and influence within the court at Kyoto (Heian-kyō) which they once enjoyed.
The name of Tachibana was bestowed on Agata-no-Inukai no Michiyo by Empress Genmei in 708. She was the wife of Prince Minu, a descendant of Emperor Bidatsu and mothered Princes Katsuragi and Sai. She later married Fujiwara no Fuhito and bore Kōmyōshi (Empress Kōmyō). In 736, Princes Katsuragi and Sai were given the surname Tachibana, renouncing their imperial family membership. They became Tachibana no Moroe and Tachibana no Sai respectively.