Joel Thomas Zimmerman (born January 5, 1981), known professionally as deadmau5 (pronounced "dead-mouse"), is a Canadian electronic music producer and DJ. Zimmerman has received seven Grammy Award nominations for his songs. He mainly produces progressive house and electro house music, though he also produces and DJs other genres of electronic music, including techno under the alias Testpilot. Zimmerman is well known for wearing custom helmets for performances and appearances, similar to Daft Punk and later inspiring Marshmello.

Zimmerman has worked with other DJs and producers, such as Wolfgang Gartner, Rob Swire, and Chris Lake. He has also collaborated with Steve Duda as the duo BSOD (Better Sounding On Drugs) and the band WTF? with Duda, Tommy Lee and DJ Aero. In 2007, he founded his own record label, Mau5trap. Deadmau5 later formed electronic music supergroups such as Kx5 with Kaskade and Rezzmau5 with Rezz. Zimmerman is currently one of the highest-paid electronic music producers in the world.

Zimmerman first gained recognition for his breakthrough 2008 album Random Album Title, which was certified gold in Canada and silver in the United Kingdom. The album included seminal releases "Faxing Berlin", "Not Exactly", and moderate chart hit "I Remember" (with Kaskade). In 2009, his fourth studio album For Lack of a Better Name was released to critical acclaim, featuring "Ghosts 'n' Stuff" (featuring Rob Swire), "Hi Friend" (featuring MC Flipside), and the critically acclaimed "Strobe". His fifth studio album, 4×4=12, released in late 2010, supported by singles "Some Chords", "Animal Rights" (with Wolfgang Gartner), "Sofi Needs a Ladder" (with Sofi), and "Raise Your Weapon" (with Greta Svabo Bech).

In 2012, Zimmerman released singles "The Veldt" and "Professional Griefers" (featuring Gerard Way) to commercial success. These singles were featured on his sixth studio album, Album Title Goes Here. Following his departure from long-time label Ultra Records, Zimmerman released his seventh studio album, While(1<2), through Astralwerks and Virgin EMI in 2014. The album's release was supported by its four singles; "Avaritia", "Seeya", "Infra Turbo Pigcart Racer", and "Phantoms Can't Hang". After a brief hiatus, Zimmerman's eighth studio album, W:/2016Album/, was released in late 2016, with singles "Snowcone" and "Let Go". He subsequently composed the score for the 2019 action film Polar, and released the singles "Satrn", "Coasted", "Fall" the same year. In 2020, "Pomegranate" and "Bridged by a Lightwave" were released. In 2024, Zimmerman released a track under his Testpilot alias, subsequently releasing "some ep".