Yuuko Ishibashi (石橋優子, Ishibashi Yūko) is a Japanese singer, born April 3, 1980, in Tokyo, with a four octave vocal range.
She is most well known for her vocal performances in Gust-produced video games such as the Ar tonelico series and Atelier Iris 3: Grand Phantasm.
She has also performed in various Japanese television advertisements and events, theater, and children's programmes.
Her debut album Haruka naru Toki no Utagoe was released January 2008.
She is the younger sister of Chie Ishibashi, better known as Chie Sawaguchi.