Seiko Yoshida is a Japanese voice actress affiliated with the agency Mausu Promotion. She was born on March 15, 1986, in Niigata Prefecture. After graduating from Niigata Prefectural Sanjo Higashi High School, she attended the International Video Media College, where she completed the voice actor course. She joined Mausu Promotion in 2008, beginning her professional career in the industry.

Yoshida has built a versatile career spanning television animation, original net animation (ONA), video games, and dubbing for foreign films and television series. In television anime, she is recognized for her performance as Kyōsuke Kamijō in the critically acclaimed series Puella Magi Madoka Magica. She also voiced the character Belphegor in Umineko: When They Cry and Toshiko Sakuma in HeartCatch PreCure!. In the fantasy action series The Testament of Sister New Devil, she took on the role of Zest, a demon who becomes a loyal maid to the protagonist, appearing in both the first season and its sequel, The Testament of Sister New Devil BURST, as well as the Departures OVA. She was also part of the cast for the anime adaptation of Mahō Sensei Negima!, playing the role of S. Du Chat in the OVA series Mahō Sensei Negima!: Mō Hitotsu no Sekai - Extra Mahō Shōjo Yue.

Her work in original net animation includes the leading role of Misaki in Toki wa Meguru: Tokyo Station, a short film created to celebrate the 100th anniversary of Tokyo Station. She also voices the character Peke-Peke in the series Moondrive. In the realm of video games, Yoshida has an extensive portfolio. She is the Japanese voice of Julia Chang in the Tekken series, a role she has performed in titles including Street Fighter X Tekken and the Netflix anime adaptation Tekken: Bloodline. She is also well-known for her long-running role as Leona Heidern in The King of Fighters series, starting from The King of Fighters XIV. Additional game credits include Suguri in 100% Orange Juice, Emily Crusoe in Another Code: Recollection, and Tohko Kirisaki in Corpse Party.

Yoshida has also been active in dubbing foreign media, providing the Japanese voice for characters such as Emily Fields in the television series Pretty Little Liars and Melanie Stryder in the film The Host. Her work demonstrates a broad range, encompassing young male characters like Kyōsuke Kamijō, strong female fighters like Julia Chang and Leona Heidern, and a variety of supporting roles across different genres. In March 2021, she announced her marriage to fellow voice actor Ryota Honda.