Marielle Ostrowski is a Belgian voice actress born on February 7, 1975, recognized for her extensive work in the French dubbing of animated series and films, particularly within the anime genre. She has been active as a singer since a young age and is an actress who passed through the Actors Studio. Her body of work demonstrates a long-standing and active career in the Belgian voice-acting community.

Ostrowski is known for providing the French voices for a wide array of characters across numerous popular franchises. One notable role is Komachi Mikumari in the series Samurai 7. She has notable recurring roles within the same franchise, such as in the world of That Time I Got Reincarnated as a Slime and its spin-off The Slime Diaries, where she voices the dryad Treyni, as well as the characters Tear and the Spirit of Light. Her involvement in these productions is part of a consistent Belgian dubbing cast often overseen by directors like Frederik Haùgness and Pierre Bodson at studios such as SDI Media.

Another significant role is that of Diana Cavendish in the Little Witch Academia franchise. She voiced the character in the original short film, the feature-length The Enchanted Parade, and the subsequent television series, with these dubs typically directed by Géraldine Frippiat, Julie Basecqz, or Dominique Wagner at studios like Sonicfilm. Her other anime voice roles are extensive and include Saeko Busujima in High School of the Dead, Pandy in Dead Leaves, Sakura Kasugano in Street Fighter Alpha Generations, and various characters in Pokémon films. In the Pokémon animated series specifically, her credits include being the first voice of Sonya in Pokémon Journeys: The Series (Season 23) and voicing the antagonist Hunter J. More recent work includes roles as Kamoto Suzu in episode 7 of Medalist, Miku in episode 8 of Medalist 2nd Season, and the mother of Fumi in episode 9 of Sanda.

Ostrowski has also lent her voice to non-anime productions, such as Diamond Tiara in My Little Pony Equestria Girls: Rainbow Rocks, and has worked on dubbing direction for projects like My Little Pony: Friendship is Magic and Robot Carnival. Her career includes roles in feature films such as Unicorn Wars, where she voiced Maman and Laura. In addition to voice acting, she has recorded audiobooks including Mauvaise fille, Le Mec de la tombe, and Le caveau de famille for Audiolib.