Zodiac is Neal Stephenson's second novel, which tells the story of an eco-terrorist uncovering a conspiracy involving industrialist pollutors and bicameral minded Satanists in the Boston Harbor. The 'Zodiac' of the title refers to the brand of inflatable motor boats the hero uses to get around the city efficiently and mount attacks.

The protagonist is modelled after eco-activist Marco Kaltoffen, who did such things as plug illegal outflow pipes as portrayed in the book.