"The Soft Weapon" is a science fiction short story written in 1967 by Larry Niven and set in his Known Space universe. It was the basis of the Star Trek: The Animated Series episode, "The Slaver Weapon" and later for Niven's novellette "The Borderland of Sol".
The story introduces the character of Nessus, a Pierson's Puppeteer who later became one of the main characters of the novel Ringworld (novel). The story is told again, from the Nessus' point of view, in "Juggler of Worlds".
First published in 1967 by If magazine and then in the short story collections "Neutron Star" and "Playgrounds of the Mind".