Kōichi Sakaguchi was born on February 10, 1968, in Tokyo, Japan. He is a Japanese voice actor and stage actor who has been active in the entertainment industry since the 1990s and is affiliated with the talent management firm 81 Produce. His career encompasses a wide range of roles in anime, video games, and live-action tokusatsu series, and he is recognized for his versatile performances in supporting and character roles.

Sakaguchi is known for several major voice roles across a variety of popular anime franchises. He is notably the voice of the recurring character Prince Hata in the long-running series Gintama, a role that has become closely associated with him. He also voiced the character in the feature films Gintama: The Movie and Gintama: The Final. In the Mobile Suit Gundam franchise, he provided the voice for Tem Ray, the father of protagonist Amuro Ray, in the series Mobile Suit Gundam: The Origin and its subsequent film compilations. He took on the role of Jack Hanma in the 2001 anime series Grappler Baki: Maximum Tournament. Sakaguchi also voiced the character Virdos in the 2023 series Summoned to Another World for a Second Time.

Many of the other specific roles requested have been verified across his extensive filmography. He voiced Pandora in Oreca Battle, Peter Westvillage in Captain Earth, Sōichirō Raimon in Inazuma Eleven, TanTan in Kirarin Revolution, and Soo in Baby Felix. Additional confirmed roles include Toraji in Sennen no Yakusoku, Raynock in Kite, Edward in MÄR, and Andy in Silk Road Kids. In the 2022 reboot of Urusei Yatsura, he voiced the character Nagisa's Dad.

Sakaguchi also had a recurring role in both the Japanese and English language Pokémon anime, where he voiced Jessie's Arbok until the Hoenn series. He also voiced the Orange Crew leader Drake's Electabuzz and later reappeared voicing Morrison's Steelix in both language versions of the series. Beyond anime, Sakaguchi has voiced characters in numerous video games, including Cid in both Final Fantasy X and Final Fantasy X-2, and Soap in the Japanese dub of Call of Duty: Modern Warfare 2. He has also performed voice work for live-action tokusatsu series such as Kamen Rider and the Super Sentai franchise, as well as dubbing roles for foreign films and animation, including Thomas & Friends and Coco.