Ingvar Even Ambjørnsen-Haefs is a Norwegian writer. He is best known for his "Elling" tetralogy: Utsikt til paradiset (1993), Fugledansen (1995), Brødre i blodet (1996), and Elsk meg i morgen (1999).

Brødre i blodet ("Blood brothers") was turned into a successful movie, entitled Elling, which received an Oscar nomination in the Best Foreign Film category in 2001. The English translation of the novel is called Beyond the Great Indoors.

His debut novel was a semi-autobiography called 23-salen ("The 23rd Row"), in which he criticized Norway's efforts to take care of psychically challenged individuals. In all his novels he has spoken the outsiders' cause, as he did in his break-through novel Hvite Niggere ("White Niggers") in 1986. The novel is about a young man who leads a life somewhat on the edges of normal society.

He is also known for the youth's book series "Pelle og Proffen" which circles around two detective teenagers, getting involved in all kinds of mysteries or crimes involving drugs, pollution and neo-Nazism among other things. He started this project after having read some of Franklin W. Dixon's books about The Hardy Boys. The books Døden på Oslo S, Giftige Løgner, and De Blå Ulvene of this series were also turned into successful movies. In 2005 the book Drapene i Barkvik ("The murders in Barkvik") appeared, about the teenager Fillip Moberg attempting to solve an axe murder in a small Norwegian village.

Ambjørnsen has received many prizes for his writing. Among them is the prize for the 80s best book for children and young adults (Pelle and Proffen books), the Tabu prize in 2001, Telenor Culture Award 2002, and the Brage Prize 1995.

His three Samson and Roberto books have become particularly popular in Russia, in part due to the illustrations by Nikolai Vorontsov, which also contribute carefully orchestrated local Russian-related colloquialisms to the stories.

He now lives in Hamburg with his German wife and translator Gabriele Haefs, where he has lived since 1985.