William Emerson Arnett (; born May 4, 1970) is a Canadian actor, comedian and producer. He is best known for his roles as Gob Bluth in the Fox/Netflix series Arrested Development (2003–2006, 2013, 2018–2019) and as the titular character in the Netflix series BoJack Horseman (2014–2020). He has appeared in films such as Let's Go to Prison (2006), Blades of Glory (2007), Semi-Pro (2008), G-Force (2009), Jonah Hex (2010), Teenage Mutant Ninja Turtles (2014) and its sequel Teenage Mutant Ninja Turtles: Out of the Shadows (2016), and Show Dogs (2018).
His deep baritone voice has landed him numerous voice acting jobs, including Danny Phantom (2004–2007), Ice Age: The Meltdown (2006), Ratatouille (2007), Horton Hears a Who! (2008), Monsters vs. Aliens (2009), Despicable Me (2010), The Nut Job (2014), Teen Titans Go! To the Movies (2018), Dolittle (2020), Rumble (2021), Chip 'n Dale: Rescue Rangers (2022) and as Batman in the Lego Movie franchise. He won an Annie Award for his role as BoJack Horseman, and was nominated for multiple Primetime Emmy Awards for his work in Arrested Development and 30 Rock. His involvement with The Lego Group continues as Fox announced him as the host of their show Lego Masters, which premiered on February 5, 2020. Since July 2020, he has co-hosted the comedy podcast SmartLess. In 2022, he starred in a six-part improvised comedy series Murderville on Netflix.