Rolf Koster is a Dutch actor and voice actor, born on February 25, 1968. He is primarily known for his extensive work providing Dutch voices for numerous anime series and animated productions.

Koster's most recognizable anime role is Kai, a main character and the leader of the Blade Sharks team, in the Dutch version of the original Beyblade series. He also voiced the character Professor in the same series. Another notable film role is Bemanningslid bril (a crew member with glasses) in the Dutch Netflix dub of the Studio Ghibli film Ponyo on the Cliff by the Sea.

His career features many other significant roles across popular anime franchises. In the Digimon series, he provided the voices for both Jim and Joe in Digimon Adventure and Digimon Adventure 02. He was a regular contributor to the Pokémon anime, voicing the character Tracey from the third season onward, the Gym Leader Morty, and Tyson in Pokémon Advance. Within the Yu-Gi-Oh! franchise, Koster voiced the complex character Bakura, including his darker alter-ego Yami Bakura, in two different Yu-Gi-Oh! television series. Additional anime roles include Mushra in Shinzo, Koji and Sloan in Medabots, and Dexter in Hamtaro.

Beyond anime, Koster's voice work extends to Dutch dubs of many other cartoons. He is known as the voice of Ron Stoppable in Kim Possible and has had roles in series such as The Kids from Room 402, Action Man, Totally Spies, He-Man, and Angela Annaconda. His work also includes providing additional voices for films like Jim Button.

In addition to performing, Koster has also worked in voice direction, as seen on the series Go! Go! Itsutsugo Land. Beyond voice acting, he is also a singer and director active in the world of musical theatre.