Kjell Ola Dahl (born 4 February 1958) is a Norwegian writer, who is sometimes known professionally as K. O. Dahl.

His writing career began with the publishing of Dødens Investeringer (Lethal Investments) in 1993 and he has subsequently authored more than a dozen novels, many short stories, several non-fiction books, and co-written two screenplays with the writer/director Hisham Zaman.

He is best known for his eleven Nordic noir crime novels which feature his Oslo detectives Frølich and Gunnarstranda. Six of these have been published in English, translated by Don Bartlett.

Speaking of his own work in Nordic Noir Dahl says ‘I’m never entirely satisfied with my work – I’m pleased, of course, that readers find things to enjoy in them, but I can always see their weaknesses all too clearly'.