Saeko Oku is a Japanese voice actor and singer affiliated with the agency AIR AGENCY. She was born on August 20, 1992, in Saitama Prefecture.

Her early career included participating as a member of the FRESH夏祭队 for an event hosted by the television network AT-X in 2015. Oku's most prominent role to date is as Mille Feuille, a member of the unit supernova, in the multimedia project and 2020 television anime series Lapis Re:LiGHTs. As part of this project, she performed in character songs with the unit supernova, including the single Trinity and RISE, as well as with the larger Lapis Re:LiGHTS Stars group on the anime's opening theme song Our STARTRAIL.

Her other voice acting credits include roles in video games. She voiced the character Isole in the Japanese version of the game King's Raid. She also provided a voice for the digital comic adaptation of Fenrir Mother and the Warm Rice Bowl.