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 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 joined 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 wears custom helmets for performances and appearances, similar to Marshmello and Daft Punk.

In 2000, an early 12" single produced on vinyl titled "I Don't Want No Other" was released by Zimmerman and Derek Caesar, under the group name Dred and Karma. A 2006 compilation album titled Deadmau5 Circa 1998–2002 was self-released under the alias Halcyon441. His debut studio album, Get Scraped, was released in 2005, with follow-up Vexillology in 2006. His breakthrough, Random Album Title, was released in 2008 and was certified gold in Canada, and silver in the United Kingdom. The album includes seminal release "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", "Sofi Needs a Ladder", and "Raise Your Weapon".

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, deadmau5 released “Quezacotl” and later a track under Testpilot, subsequently releasing "some ep".