Per Fredrik Wahlöö – in English translations often identified as Peter Wahloo – was a Swedish author. He is perhaps best known for the collaborative work with his partner Maj Sjöwall on a series of ten novels about the exploits of Martin Beck, a police detective in Stockholm, published between 1965 and 1975. In 1971, The Laughing Policeman won an Edgar Award from the Mystery Writers of America for Best Novel. Wahlöö and Sjöwall also wrote novels separately.

Maj Sjöwall was a Swedish author and translator. She is best known for her books about police detective Martin Beck. She wrote the books in collaborative work with her partner Per Wahlöö.