Matti Yrjänä Joensuu (born 1948) was a Finnish writer of crime fiction. He was awarded the State’s Literature Prize (1982), Vuoden johtolanka prize (1985, 1994, 2004), and he was nominated for two Finlandias. He received the Martin Beck Award in 1987. He graduated as a police in 1973 and worked as a crime investigator at the Helsinki police station’s violence group.

Joensuu wrote several novels about the personal life and work of policeman Timo Harjunpää. He is a very credible and pleasant man, who treats the criminals as humanely as his own family