Masashi Hirose is a Japanese voice actor born on November 6, 1947, in Osaka Prefecture. Throughout his career, he was affiliated with the talent management firm Production Baobab. His voice was a familiar presence in Japanese animation for over four decades, from the 1970s until his health led to a pause in his activities in 2014.

Hirose's career is marked by a wide range of supporting and character roles, often bringing to life figures of authority, seasoned warriors, and gruff but memorable personalities. He is perhaps best known for his portrayal of the iconic Zeon officer Ramba Ral in the original Mobile Suit Gundam (1979), a role that established him as a fan favorite and one he would reprise in various film compilations and video games for years to come. This connection to the Gundam franchise continued with roles like Master O in Gundam Wing, Katokk Alzamille in After War Gundam X, and Sahib Ashman in Gundam SEED, culminating in the affectionate tribute character Mr. Ral in Gundam Build Fighters (2013).

Beyond Gundam, Hirose became a regular presence in the works of director Ryosuke Takahashi, particularly in the realistic mecha genre. He voiced Destin in Fang of the Sun Dougram and had multiple roles in the Armored Trooper Votoms universe, including Kan Yu in the original television series, Lada Niva in the Big Battle OVA, and Dennis in the Case;Irvine OVA. His other notable mecha anime roles include Gosterro in Blue Comet SPT Layzner and Stinger in Getter Robo: Armageddon. In the long-running Kinnikuman series, he was the voice of the character Rikishiman.

His versatility extended across many of Japan's most popular series. He made numerous appearances in Detective Conan, played roles in Cowboy Bebop, Samurai Champloo, and Paranoia Agent, and was a regular presence in long-running franchises like One Piece, where he voiced Riku Dold III, and Fairy Tail as the villain Hades. He also took on significant roles in major productions such as Fate/zero as Risei Kotomine and in the Umineko no Naku Koro ni series as Hideyoshi Ushiromiya. In addition to anime, Hirose was active in dubbing foreign films and television series, providing the Japanese voice for Apu Nahasapeemapetilon and Sideshow Mel in The Simpsons, as well as serving as the regular Japanese dubbing voice for Marvel Comics icon Stan Lee in his film cameos.

In September 2014, Hirose was hospitalized for an illness, leading him to step away from voice acting to focus on his recovery. His ongoing roles were subsequently taken over by other actors, including Katsuhisa Hōki in Gundam Build Fighters Try, Banjō Ginga in One Piece, and Akio Ōtsuka in In Search of the Lost Future. While he has not returned to active voice work since, his extensive body of work, particularly his portrayal of Ramba Ral and his many contributions to the real robot genre, remains a significant part of anime history.