Jóhann was born on 19 September 1969 in [[Reykjavík]], Iceland to Jóhann Gunnarsson, a maintenance engineer who worked for [[IBM]], and Edda Thorkelsdóttir.<ref name=NYTObit>{{Cite news|url=https://www.nytimes.com/2018/02/12/obituaries/johann-johannsson-award-winning-movie-composer-dies-at-48.html|title=Johann Johannsson, Award-Winning Movie Composer, Dies at 48|last=Codrea-Rado|first=Anna|date=12 February 2018|work=The New York Times|access-date=14 February 2018|language=en-US|issn=0362-4331|archive-date=14 February 2018|archive-url=https://web.archive.org/web/20180214001737/https://www.nytimes.com/2018/02/12/obituaries/johann-johannsson-award-winning-movie-composer-dies-at-48.html|url-status=live}}</ref> He learned the piano and trombone from the age of 11, but had given them up during his teenage years.<ref name=NYTObit/> Jóhann attended the [[University of Iceland]], where he studied languages and literature.<ref name=NYTObit/>
Jóhann started his musical career in the late 1980s in the proto-[[shoegaze]]-influenced band Daisy Hill Puppy Farm, who released a couple of EPs which were played by British DJ [[John Peel]] and received a fan letter from [[Steve Albini]].<ref name="grapevine"/> He went on to work as a guitarist and producer playing in Icelandic [[indie rock]] bands, like Olympia, [[Unun (band)|Unun]] and Ham.<ref name="PF"/> In 1999, Jóhann co-founded [[Kitchen Motors]];<ref name="PF">{{cite web|url=https://pitchfork.com/news/johann-johannsson-dead-at-48/|title=Jóhann Jóhannsson Dead at 48|publisher=PitchFork|date=10 February 2018|author1=Blais-Billie, Braudie|author2=Minsker, Evan|access-date=11 February 2018|archive-date=10 February 2018|archive-url=https://web.archive.org/web/20180210235315/https://pitchfork.com/news/johann-johannsson-dead-at-48/|url-status=live}}</ref> a think tank, art organisation and music label that encouraged interdisciplinary collaborations between artists from [[punk rock|punk]], [[jazz]], [[Classical music|classical]], [[Heavy metal music|metal]] and [[electronic music]]. His own sound arose out of these musical experimentations.<ref name="grapevine">{{cite web|url=https://grapevine.is/culture/music/2016/09/09/history-of-johann-the-composers-path-through-the-reykjavik-scene/|title=History Of Jóhann: The Composer's Path Through The Reykjavík Scene|date=9 September 2016|publisher=Grapevine.is|access-date=12 February 2018|archive-date=22 October 2016|archive-url=https://web.archive.org/web/20161022214837/http://grapevine.is/culture/music/2016/09/09/history-of-johann-the-composers-path-through-the-reykjavik-scene/|url-status=live}}</ref>
