Sada Yacco or Sadayakko (川上 貞奴, Kawakami Sadayakko^?, July 18, 1871 - December 7, 1946) was a Japanese actress and dancer.

Born in Tokyo as Sada Koyama, Sadayakko was trained as a geisha and came to the attention of the prominent Japanese politician Itō Hirobumi, who took an interest in furthering her education. In 1894 she married the actor Otojiro Kawakami, to whom she had been introduced by Hirobumi. She would later be known as Sada Yacco.

Sadayakko performed in the company her husband founded, The Kawakami Theatre, when it was considered improper for women to perform on stage with men. In 1899, the troupe toured America and Europe, and became the first Japanese theater company to be seen in the west. Performances were held in San Francisco, and New York City in the United States, as well as at the 1900 Exposition Universelle in Paris (with theatrical lighting there done by Loie Fuller) and several other European cities.

A few years after the death of her husband in 1911, Sadayakko became the lover of businessman Momosuke Fukuzawa (1868–1938), and they lived together like a married couple, although Fukuzawa's wife was still living. Their restored home is now a museum. After 1918, Sadayakko ceased touring and opened a textile concern in Nagoya. She also founded a children's drama school and children's theater in Tokyo and continued to perform occasionally in Japan.