The Principia Discordia is the first published Discordian religious text. It was written by Greg Hill with Kerry Wendell Thornley and others. The first edition was printed using Jim Garrison's Xerox printer in 1963. The second edition was published under the title Principia Discordia or How The West Was Lost in a limited edition of five copies in 1965. The phrase Principia Discordia, reminiscent of Isaac Newton's 1687 Principia Mathematica, is presumably intended to mean Discordant Principles, or Principles of Discordance.

Discordianism is a belief system based around Eris, the Greek goddess of strife and discord, and variously defined as a religion, new religious movement, virtual religion, or act of social commentary; though prior to 2005, some sources categorized it as a parody religion. It was founded after the 1963 publication of its holy book, Principia Discordia, written by Greg Hill with Kerry Wendell Thornley, the two working under the pseudonyms Malaclypse the Younger and Omar Khayyam Ravenhurst.