Discordianism is a religion based on worship of the Greek goddess Eris, known to the Romans as Discordia, and appearing in different forms in many religions around the world. It is also heavily influenced by an absurdist interpretation of Rinzai Zen Buddhism, and Taoism. Discordianism has been describe alternately as "a joke masquerading as a religion", and "a religion masquerading as a joke"; and is considered the world's first "postmodernist" religion.
Discordianism was founded in the Year of Our Lady 1957 by Lord Omar Khayyam Ravenhurst aka Kerry Wendel Thornley, and Malaclypse the Younger aka Gregory Hill; while sitting in a bowling ally in East Whittier, CA, drinking coffee. They claimed to have both had a revelation of the goddess at the same time (possibly under the influence of other substances), at which time a talking ape revealed to them the secret of the Sacred Chao.
The original holy text is The Principia Discordia, written by Thornley and Hill; and published in 1965. There have been multiple editions since then, each different (in large ways or small) from the last, as is fitting for any Discordian scripture.
The religion described in the Principia is further expanded upon in The Illuminatus! Trilogy, by early Discordians Robert Anton Wilson and Robert Shea; who provided a larger mythology and context for it in their fictional work.
Other works further expanding upon or providing a context for the religion: Historia Discordia, a history of the founding of Discordianism, and some of the figures involved in its early days; compiled and edited by Adam Gorightly, and published in 2014.
The Black Iron Prison, a collaborative effort edited by SAI Peregrinus, and published in 2007; as an attempt to update the Principia for a new era.
Chasing Eris, by Brenton Clutterbuck, published in 2019; as a sort of gonzo journalist view of the Discordian community at the time it was written.
Zen Without Zen Masters by Camden Benares, published in 1977. Although more concerned with Zen Buddhism than Discordianism; Benares was part of the early Discordian community, and there are a number of references to Discordian figures and scriptures in it; and it has strongly influenced later Discordian writing, including Illuminatus!