Yōko Asada is a Japanese voice actress born on May 23, 1969, in Hyōgo Prefecture. She is affiliated with the talent management firm 81 Produce. Asada began her voice acting career in the early 1990s, with her debut role being Mia Ausa in the 1992 video game Lunar: Silver Star Story. During the 1990s, she was a member of the voice acting unit Radish Roxs, alongside fellow voice actors Tomoko Konishi, Manabi Mizuno, Chiaki Morita, and Kanako Okada.

Asada is known for a wide range of roles across television anime, original video animations, and video games. In television, she is recognized for the role of Alice Mizuki in the seminal 1998 series Serial Experiments Lain. She also voiced Juri Katō in Digimon Tamers, Roulette Boy in Gregory Horror Show, and the Queen of Seijuu in Koi Suru Tenshi Angelique: Kokoro no Mezameru Toki. Other television credits include Aino Nozomi in D4 Princess, Linda in Ippatsu Kiki Musume, Hiromi Shinohara in You're Under Arrest, Botan in the original Pokémon series, and guest roles in long-running series such as Detective Conan. She also played Akiko Hoshino in Aria the Animation, Roseno in Kyo Kara Maoh!, and a young Ayuko in Golden Boy. Later television work includes roles in Heartcatch Pretty Cure! and the Angelique franchise.

Her work in original video animations is extensive. She voiced the titular character Alice in Alice in Cyberland, Mari in My Dear Marie, and Natasha in Dragon Knight: Wheel of Time. She portrayed multiple roles in the Cool Devices anthology series, including Cat Girl, Marino Ōkura, and Minako. For the OVA Parade Parade, she not only voiced the character Kaori Shiine but also performed the theme song. Additional OVA roles include Casa Clover XVII in Wild Cardz, Sakurako Sugimoto in Dōkyūsei 2 Special: Sotsugyōsei, and Asuka Kashiwagi in Mystery of the Necronomicon. Asada voiced Lorna Endō in both the éX-Driver OVA series and its subsequent theatrical film éX-Driver the Movie. She was also a recurring presence in the Angelique OVA series, voicing Angelique Collet in Angelique: Shiroi Tsubasa no Memoir and Angelique: Seichi Yori Ai o Komete. She performed the role of Plumerock in Tournament of the Gods and Harumi Sugino in Refrain Blue.

In the field of video games, Asada is known for her role as Mia Ausa in Lunar: Silver Star Story, a role she originated. She also voiced Tifa Lockhart in the arcade version of Ehrgeiz, Will in Princess Quest, Leeza in Arc the Lad II, and Rinka Yoshino in Samurai Shodown: Warriors Rage.