Jóhann Gunnar Jóhannsson (Icelandic pronunciation: [ˈjouːhan ˈjouːhansɔn]; 19 September 1969 – 9 February 2018) was an Icelandic composer who wrote music for a wide array of media including theatre, dance, television, and film. His work is stylised by its blending of traditional orchestration with contemporary electronic elements.

Jóhann released solo albums from 2002 onward. In 2016, he signed with Deutsche Grammophon, through which he released his last solo album, Orphée. Some of his works in film include the original scores for Denis Villeneuve's Prisoners, Sicario, and Arrival, and James Marsh's The Theory of Everything. Jóhannsson was nominated for an Academy Award for Best Original Score for both The Theory of Everything and Sicario, and won a Golden Globe for Best Original Score for the former. He earned a second Golden Globe nomination for Arrival. He was a music and sound consultant on Mother!, directed by Darren Aronofsky in 2017. His scores for Mary Magdalene and Mandy were released posthumously.

His only directorial work, Last and First Men, premiered at the Manchester International Festival in 2017, where he also performed the score live with the BBC Philharmonic Orchestra.