R. Martin Klein is an American voice actor known for his extensive work in anime dubbing and animated productions. Active in the industry since 1981, he has also been credited under the names Robert Martin Klein, Robert Klein, Bob Klein, and occasionally as Bob Marx for earlier dubbing work during the 1990s. In addition to voiceovers, Klein has worked in theater and film productions.

Klein is perhaps best known for his long-standing association with the Digimon franchise. He provided the voice for the character Gomamon and its evolutions, including Ikkakumon, across multiple series and films. His work in this role spans from the original Digimon: Digital Monsters and its sequel, through Digimon Data Squad, Digimon Fusion, and the later theatrical releases Digimon Adventure tri. and Digimon Adventure: Last Evolution Kizuna. His filmography also includes a wide range of other notable anime roles. He voiced Katsuhiko Jinnai in El Hazard, Fukurou in Noein, and Mr. Me-Mania in the film Perfect Blue. He also played Flint Hammerhead in Flint the Time Detective, Ivan Whisky as Cyborg 001 in Cyborg 009, and Marumaro in Blue Dragon. Additional credits include roles in FLCL, Mobile Suit Gundam: The 08th MS Team, Zatch Bell!, and MÄR.

Beyond anime, Klein's voice work extends to western animation and other media. He voiced Iggy D'Iguana and other characters in the series Animalia and was the voice of Edison the Firefly in five LeapFrog DVDs, credited as Robert Mark Klein. He also provided voices for the Lego Star Wars special The Padawan Menace, playing Chancellor Palpatine and Darth Sidious. In live-action, he voiced the character Seymour in Power Rangers in Space. His contributions to video games include roles in the.hack series as Harald Hoerwick and Marlo, as well as Lias Warren in Star Ocean: First Departure.