Yamauchi Kazutoyo (?? ?? (???? ????)), also spelled Yamanouchi (1545/1546? – November 1, 1605), was born the son of Yamanouchi Toyonao in Owari Province at the end of the Sengoku period of Japan.
Kazutoyo held the title of Tosa no kami.
Kazutoyo built Kochi Castle.
His life spanned the closing years of the Sengoku period, the Azuchi–Momoyama period, and the beginning of the Edo period.
Just four years after he became Lord of Tosa, Kazutoyo died without issue aged around 60, and was succeeded as Lord of Tosa by his nephew Tadayoshi.
When he was still a 400-Koku lord many of great people when child was entrusted to him, like Kuroda Nagamasa was hostage of Oda Nobunaga and Toyotomi Hidetsugu was taught by him.