William Emerson Arnett (/ɑːrˈnɛt/; born May 4, 1970) is a Canadian and American actor and comedian. He is widely known for his roles as Gob Bluth in the Fox/Netflix sitcom Arrested Development (2003–2006, 2013, 2018–2019) and the titular character in the Netflix animated series BoJack Horseman (2014–2020). He has received nominations for seven Primetime Emmy Awards and three Screen Actors Guild Awards.

Arnett was Emmy-nominated for his recurring role as Devon Banks in the NBC sitcom 30 Rock (2007–2013). He starred in the NBC sitcom Up All Night (2011–2012), the CBS sitcom The Millers (2013–2014), and the Netflix mystery series Murderville. He has also starred, co-created, and executive produced the Fox sitcom Running Wilde (2010–2011) and the Netflix comedy-drama series Flaked (2016–2017).