Matti Yrjänä Joensuu (31 October 1948– 4 December 2011)[1][2] was a Finnish writer of crime fiction.

The protagonist of Joensuu's novels, the senior constable Timo Harjunpää, is a sympathetic character who is equally human about the criminals he encounters in his work as his family.

Joensuu's work has been translated into English, Bulgarian, Dutch, Italian, Norwegian, French, Swedish, German, Slovak, Danish, Hungarian, Armenian, Russian and Estonian.

Joensuu has written 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, which consists of Timo, his wife Elisa and three children (Valpuri, Pipsa and Pauliina).