Tetsuya Iwanaga is a Japanese voice actor born on June 24, 1970, in Tokyo's Musashino City. He began his career in the 1990s after training at the Japan Narration Acting Institute. Throughout his career, he has been affiliated with several talent management firms, including ARTSVISION and Max Mix, and has worked as a freelancer since 2012.

Iwanaga has built a substantial career with a wide range of roles in anime, OVA, and video games. One of his most prominent and enduring roles is that of Kensuke Aida in the landmark series Neon Genesis Evangelion, a character he has voiced since 1995, including in the recent Rebuild of Evangelion film series. He is also known for playing Makoto Mizuhara in The Mysterious World of El-Hazard and its sequels, and Asuka Tachibana in s-CRY-ed. In the popular franchise Yu-Gi-Oh! Duel Monsters, he voiced the antagonist Marik Ishtar.

Many of the roles listed by the user are verified as part of his extensive filmography. These include his parts as Masao Sera in Nightmare Campus, Yoneda in High School Jingi, Tomohisa Kaname in Puella Magi Madoka Magica, Masayuki Tsutsumi in Seikimatsu Darling, Juukyuurou Satomi in High School Aurabuster, Sei-Lan across various Angelique series and OVAs, Daisuke Ooyama in Goal FH, Otaku in Kyōryū Bōkenki Jura Tripper, Kuro in Tama and Friends, Kazuhiro Sasamoto in Hōkago no Tinker Bell, Superstarman in Tottemo! Luckyman, Lan Svendsen in Locke the Superman: Mirror Ring, Tohru Takamura in Sprite: Between Two Worlds, Trapp in Fortune Quest L, J.J. in Fake, Tsutomu in Birdy the Mighty, and Junji Kiyama in Teppen. The user's mention of Christopher Chiaki in Garzey's Wing is also confirmed.

Beyond these roles, Iwanaga's career includes other significant performances. In video games, he is known for voicing Ken Masters in the Street Fighter Alpha and EX series and the protagonist Kinnosuke Kazama in the Langrisser series. In television anime, he has had recurring roles in long-running series such as the role of鬼蜘蛛丸 (Kumogakure) in Nintama Rantarō and several guest characters in Case Closed.

Throughout his career, Iwanaga has participated in recurring collaborations. He voices the character Sei-Lan across multiple installments of the Angelique franchise. He was also part of a voice-acting unit called "Ouji to Atama" (The Prince and The Head) with fellow voice actor Tomokazu Seki until the year 2000. In the 1990s, he was a member of a unit called "GET DO`S" along with Kazuyuki Okitsu, Showtaro Morikubo, and others.

A notable aspect of his casting is that he originally auditioned for the role of protagonist Shinji Ikari in Neon Genesis Evangelion but was instead cast as Kensuke Aida, a role that would become one of his most famous.