Ion Dissonance is a mathcore band from Montreal, Quebec, Canada. They have often been compared to The Dillinger Escape Plan, Beecher and Meshuggah.

Ion Dissonance are known for their technical metalcore/mathcore style but changed to a more heavy, groove based style with the release of their 2007 album Minus The Herd.

Antoine Lussier and Sebastien Chaput formed Ion Dissonance during the late summer of 2001 with the intention of creating metal that was more complex and daring than what they have done before. JF Richard would join shortly after on drums. With these members, their sound started to take shape, but they still required a few more individuals to fill some parts. To that end they recruited Gabriel McCaughry (vocals) and Sebastien Painchaud (bass guitar). Upon completing their first official line-up, the band released a demo CD named .357, which was quickly put together in 2002 for promotional purposes to various zines, labels and individuals around North America. This demo is now out of print but was released on mp3.com. Within no time, they received positive reviews and reactions. In this short time, they had to pick an appropriate label to support them and soon release their first LP. They decided to stay with Willowtip Records (Cacophonous Records in Europe). The line-up was changed when Sebastien Painchaud was replaced by their second bassist, Miguel Valade. With this change, they started playing their first major shows as the opening act for such bands as The Dillinger Escape Plan, Every Time I Die, Daughters, Misery Index, The End, and The Black Dahlia Murder.

During April 2003 they started the recording process for their first LP, Breathing is Irrelevant with sound-engineer Yanick St-Amand (Neuraxis, Martyr, In Dying Days), the album was completed in June 2003, and it came out in October 2003. It received many favourable reviews from a number of webzines and magazines including Metal Maniacs, Terrorizer and Unrestrained!.

In 2004, they started their first big tour including shows along US East Coast with Forever Is Forgotten, which was successful due to the positive reaction from the crowds; shows from the East to West Coast of Canada with fellow Canadians The End; this was then followed by the Maryland Deathfest. Subsequently, bassist Miguel Valade was replaced by Xavier St-Laurent.

After the release of their second album Solace on Abacus Recordings, Ion Dissonance once again toured Canada and the US. On Tuesday, June 20, 2006, Gabriel announced his departure from the band, citing personal issues and different interests in music. In October 2006, the band introduced their new vocalist, Kevin McCaughey, formerly of Shaolin.

In April 2007, Ion Dissonance recorded their album, Minus The Herd. While the album was scheduled for release on June 5, 2007. There has been some controversy over this album dealing with the differences between old and new vocalist. The newer is generally considered to be heavier and missing some of the "chaos" from the older albums. After being in Western Europe, they returned to Canada and the US for the Summer Slaughter Tour.