Yuko Yamaguchi (山口 裕子 Yamaguchi Yūko, born October 24) is a Japanese character designer and illustrator, who is well-known as the third character designer of Hello Kitty.
Yamaguchi was born in Kōchi, Kōchi, Japan. She attended Joshibi University of Art and Design where she studied industrial design. Yamaguchi joined Sanrio in 1978. In 1980 she became the third Hello Kitty designer. She has been the main Hello Kitty designer for much of the character's history.
Aside from Hello Kitty, Yamaguchi is also the producer of the character franchise Jewelpet since 2008. She also did the illustration for TV Asahi's official mascot, Go-Chan.