Billy Regan is the professional pseudonym for William Regan Timoney, an American actor, voice actor, director, and script writer with a career spanning several decades in the anime dubbing industry. He entered the field of anime dubbing in 1991 and has been credited under the names Bill Timoney and Billy Regan throughout his career.

Regan has contributed his voice to a wide array of anime series and films. Among his notable roles is Hajime Murata, the observant narrator and central human character in the science fantasy series Shingu: Secret of the Stellar Wars. He also voiced dual roles in the Voltage Fighter Gowcaizer OVA, providing the voices for the protagonist Ryo Asahina and the male persona of the character Prato.

He is also known for his work in the Pokémon franchise. In the television special The Mastermind of Mirage Pokémon, Regan voiced both Dr. Yung, the scientist who invented the Mirage System, and his villainous alter ego, the Mirage Master. His other anime roles include Kazuhiro Hasukawa, the caring older brother in the comedy Here is Greenwood.

Beyond acting, Regan has made significant contributions to anime localization as a director and script adapter. He has adapted scripts and directed dubbing sessions for several series, including Gravitation, Genshiken, and Gokudo: Swordsman Extraordinaire. He has also directed recording sessions for episodes of Comic Party and Record of Lodoss War. He is perhaps best known for voicing the hero Parn in the classic fantasy series Record of Lodoss War and its sequel.