Bertil Mårtensson (born 1945 in Malmö, now living in Helsingborg) is a Swedish author of science fiction, crime fiction and fantasy and also an academic philosopher. In this capacity he has been assistant professor at Umeå university, where he was also Chair of the department 1988-93, and in Lund.
Since his youth, Mårtensson has written mainly science fiction short stories and novels, and a lengthy fantasy work in three volumes published in 1979–83 and in a revised edition in 1997.
His work has in style and themes been compared by Swedish critics to those of Clifford D. Simak, Theodore Sturgeon, Arabian Nights and J. R. R. Tolkien. The Scandinavian flavour has also been emphasized. Those familiar with the Scandinavian type of troll as in Ibsen & Grieg's Peer Gynt with In the Hall of the Mountain King or the trolls of John Bauer will feel at home in his fantasy series, it has been said.
He began his career as a highly active science fiction fan, co-editing Science Fiction Forum with John-Henri Holmberg and Mats Linder in the sixties, and later himself in the nineties. He has also contributed many short stories and articles to Swedish science fiction fanzines, and been Guest of Honor at several national science fiction conventions.