Youko Matsuoka is a veteran Japanese actress and voice actress born on October 20, 1954, in Tokyo. She is affiliated with the talent agency 81 Produce. Her career in entertainment began on stage as a theatrical actress before she transitioned to voice acting, with her first anime role being Jim in the 1977 television series Wakakusa no Charlotte.

Throughout her extensive career, Matsuoka has demonstrated a wide vocal range, frequently cast in roles that showcase her versatility. She is particularly well-known for portraying energetic young boys as well as mature, sometimes妖艳 (yōen, meaning alluring or mysterious), women. This duality is a hallmark of her professional work. One of her earliest leading roles as a boy was Sasuke Sarutobi in the 1979 series Manga Sarutobi Sasuke. She continued in this vein with characters like Kenta Sanada, the young protagonist of GoShogun (1981), and Daichi Haruka, the hero of Madō King Granzort (1989). Her filmography from this period also includes Akru in Jungle Book: Shōnen Mowgli (1989) and Kenji Kokuhō in Moeru! Oniisan (1988).

The 1990s brought further prominent roles. She voiced Karl Lichter von Randoll in the Future GPX Cyber Formula series and took on the title role of Kitaro in the fourth iteration of the long-running Gegege no Kitarō franchise in 1996. She also joined the cast of One Piece in 1999, providing the voice for the pirate Alvida, a role she has continued to play in subsequent productions including the 2019 film One Piece: Stampede. Other notable credits from this decade include Queen Sayuri Kinniku and Konita in Kinnikuman: Kinnikusei Ōi Sōdatsu-hen (1991) and the title character Huck in Huckleberry Finn Monogatari (1994).

In the 2000s and beyond, Matsuoka's career continued to flourish. She played Ginga Izumo in Gear Fighter Dendoh (2000), the strategically minded young go player Kōsuke Ochi in Hikaru no Go (2001), and Maria Graceburt in the My-Otme franchise. She also lent her voice to Madame Christmas in Fullmetal Alchemist: Brotherhood (2009), Grandma in the Chinese-Japanese co-production Spiritpact (2017), and Queen Metaria in Sailor Moon Crystal (2014). A recurring theme in her later career is reprising roles from earlier decades, such as Teitania da Montewells in new Armored Trooper Votoms projects.

Beyond anime, Matsuoka is also active in dubbing foreign films and television series. A prominent example is her long-running role providing the Japanese voice for Captain Kathryn Janeway in the series Star Trek: Voyager. Her work in dubbing and anime has seen her collaborate frequently with other voice actors, including Kōichi Yamadera, Noriko Hidaka, and Shūichi Ikeda, among others.