Kenneth W. James
From the Super Mario Wiki
Kenneth W. "Kenny" James is an American voice actor for Bowser. His debut was in Super Mario Strikers, where he voiced Bowser and the Super Team and has voiced Bowser regularly since Super Mario Galaxy. Despite this, Scott Burns' (James' predecessor) voice was still heard in subsequent series titles such as Mario Strikers Charged, Mario Party DS, Mario Super Sluggers and Mario & Sonic at the Olympic Winter Games.
In 2009, James returned to voice Bowser in Mario & Luigi: Bowser's Inside Story and New Super Mario Bros. Wii. In 2010, James continued to voice Bowser in Super Mario Galaxy 2 and Mario Sports Mix. As of now, he is the only voice actor of Bowser and continues to voice the character, as well as Dry Bowser (as of Mario Kart Wii), Paper Bowser, Mini Bowser, Dark Bowser, and Dreamy Bowser.
Kenneth W. James was born in Nevada, but grew up in Texas. In 1988, James began singing and was later the lead singer in several bands before becoming active in community theater. In 2001, James started doing voiceover work, with Bowser being one of the first roles for which he auditioned and was chosen.
He has been a fan of video games since playing the arcade game Pong. His first Nintendo games were Super Mario Bros. and Duck Hunt on the NES, and he later played more games on that system. Outside of video games, James has voiced characters in two different online Doctor Who audio series and has done several other audio books. When portraying Bowser, James often makes claw hands to help him sound like a monster.