The episodes of the Hellsing anime series premiered on Fuji Television on October 10, 2001 and ran for thirteen episodes until its conclusion on January 16, 2002. Produced by Gonzo, directed by Umanosuke Iida and written by Chiaki J. Konaka, the episodes are based on the characters and settings of the Hellsing manga series by Kouta Hirano but lead through a different story. The episodes as a whole detail the works of the Hellsing Organization, a secret anti-paranormal unit under the command of Sir Integra Wingates Hellsing, and its various operatives including the vampire Alucard and his fledging partner, ex-policewoman Seras Victoria.
The series is licensed for English language release in North America by Geneon Entertainment, in the United Kingdom by ADV Films and in Australia by Madman Entertainment. Geneon's English dub of the series aired in the United States on Starz!'s Encore Action channel from October 4, 2003 to December 27, 2003.
Satelight and Geneon Entertainment began production of an original video animation (OVA) series in 2006. Entitled Hellsing Ultimate, the OVA episodes more closely follows the source manga and differs from the first series with the divergence of the former based on the latter's episode 5 and 6 as it was not possible to put in Millenium as the antagonists in the TV version. In addition, the inclusion of The Major and his Millenium officers are the main antagonists in Hellsing Ultimate unlike the TV adaptation. The first fifty minute episode was released released to Region 2 DVD in Japan on February 10, 2006, with four episodes released as of February 2008. It is licensed for release in the United States by Geneon USA, with the first episode released on December 5, 2006. Geneon USA stopped self-distribution of its titles in 2007, but remains the series' licensor with Funimation Entertainment taking over its North American distribution of the episodes. Funimation is releasing the fourth episode and re-releasing the first three episodes on September 23, 2008.
Two pieces of theme music are used for the first Hellsing anime series. "Logos Naki World" by Yasushi Ishii is used as the opening theme while Mr. Big's "Shine" is used for the ending theme. For the OVA episodes, the ending of each episode features various instrumental pieces composed by Hayato Matsuo and performed by the Warsaw Philharmonic Orchestra.