Hajime Koseki was a Japanese voice actor and actor from Yamagata Prefecture, born on May 7, 1932. He passed away on November 18, 2013, at the age of 81. Throughout his extensive career, which spanned from the 1950s until his death, he was active in various fields including anime, video games, and tokusatsu. At the end of his life, he was affiliated with the talent management firm 81 Produce.

Koseki's work in anime included a range of supporting and guest roles. He is known for providing the voice of Gehlen in Space Battleship Yamato III and Kirin in Yu Yu Hakusho. Other notable anime credits include the role of Umi Akatsuki in the 1994 animated film Ninku: Knife no Bohyō, Takeshi Suyama in the original video animation Angel Cop, and Chief Garner in the 16-episode series Dirty Pair Flash. In the 1988 animated film Kosuke-sama, Rikimaru-sama: Konpeitō no Ryū, he voiced the character Michael Commando. He also contributed his voice to Studio Ghibli's 1994 film Pom Poko.

Beyond anime, a substantial part of Koseki's career was dedicated to voice-over work, or fukikae, for foreign films and television series. He provided the Japanese voice for characters in numerous Western blockbusters and acclaimed dramas. Among his many dubbing credits were roles in films such as The Godfather, Amadeus, and Schindler's List. He also lent his voice to major Hollywood productions like Heat, The Quick and the Dead, and Batman Returns. His dubbing work extended to the James Bond film series, with credits including From Russia with Love and Goldfinger. He also contributed to tokusatsu productions, providing voice work for series in the Super Sentai franchise, such as Chouriki Sentai Ohranger and Seijuu Sentai Gingaman.