Clarkesworld Magazine is an American online fantasy and science fiction magazine. It released its first issue October 1, 2006, and has maintained a regular monthly schedule since, publishing fiction by authors such as Elizabeth Bear, Kij Johnson, Caitlin R. Kiernan, Sarah Monette, Catherynne Valente, Jeff VanderMeer and Peter Watts.

A science fiction magazine is a publication that offers primarily science fiction, either in a hard-copy periodical format or on the Internet. Science fiction magazines traditionally featured speculative fiction in short story, novelette, novella or novel form, a format that continues into the present day. Many also contain editorials, book reviews or articles, and some also include stories in the fantasy and horror genres.