Seizō Katō was a Japanese actor, voice actor, and narrator born in Tokyo on February 14, 1927. He was active in the entertainment industry from 1956 and was affiliated with the talent agency Haikyo, the Tokyo Actor's Consumer's Cooperative Society. Katō passed away on January 17, 2014, at the age of 86 in Itabashi, Tokyo.

Katō is widely recognized for his roles across numerous anime series, original video animations, and feature films. He was notably the voice of the characters Ittetsu Hoshi across multiple iterations of the sports series Kyojin no Hoshi (Star of the Giants), including the original 1968 television series and subsequent films. In the mecha genre, he provided the voice for Dr. Hamaguchi in Chōdenji Machine Voltes V and Professor Genrai Yuri in Blocker Gundan 4 Machine Blaster. He played the role of Hazanko in the space western Outlaw Star and voiced Gamo Whisky in Cyborg 009: The Cyborg Soldier. His other anime television credits include Kogan Iwamoto in Shigurui: Death Frenzy, Fuji in The Gokusen, and a recurring role as Police Chief Kiyonaga Matsumoto in the long-running series Detective Conan.

In the realm of animated films and OVAs, Katō portrayed Count Magnus Lee in the original 1985 Vampire Hunter D, a role that became one of his most celebrated performances. He also voiced Lord Helmuth in the 1984 film SF New Age Lensman, the Wolf in the 1978 film Ringing Bell, Inspector Zenigata in the 1987 film Lupin III: The Fuma Conspiracy, and the character Okaa-san in the acclaimed 2003 film Tokyo Godfathers. Additional OVA work included roles in Crying Freeman, Gunsmith Cats, The Guyver: Bio-Booster Armor, and Hyper Doll.

One of his most significant and defining roles was that of the Decepticon leaders Megatron and Galvatron in the original Transformers television series. He voiced these characters from the first series through Transformers: The Headmasters, and also voiced Devastator. It was reported that he later voluntarily turned down the opportunity to reprise the role of Megatron for the 2007 live-action Transformers film, stating, I no longer have the same level of confidence as I did then.

Beyond animation, Katō had an extensive career in tokusatsu productions and dubbing foreign films. In the Super Sentai series, he voiced several emperors and villains, including Earth Emperor Zeba in Hikari Sentai Maskman and Great Satan in Kyoryu Sentai Zyuranger. He also played General Jark in Kamen Rider BLACK RX. For Japanese dubs of foreign media, he voiced Odo in Star Trek: Deep Space Nine, Gurney Halleck in the film Dune, Cleo McDowell in Coming to America, and Marley in Home Alone. In live-action Japanese cinema, he provided the ADR for Koyata Hatakeyama in Akira Kurosawa's Ran after the original actor was injured.