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 in the realm of anime. She is known for providing the French voices for a wide array of characters across numerous popular franchises.

Ostrowski has notable recurring roles within the same franchise. In the world of That Time I Got Reincarnated as a Slime and its spin-off The Slime Diaries, 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. These dubs were typically directed by Géraldine Frippiat, Julie Basecqz, or Dominique Wagner at studios like Sonicfilm.

In the Pokémon animated series, her credits include being the first voice of Sonya in Pokémon Journeys: The Series (Season 23) and voicing the antagonist Hunter J. Her other anime voice roles are extensive and include Saeko Busujima in High School of the Dead, Pandy in Dead Leaves, Komachi in Samurai 7, Sakura Kasugano in Street Fighter Alpha Generations, and various characters in Pokémon films. She 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. Her body of work demonstrates a long-standing and active career in the Belgian voice-acting community.