The Cathedral and the Bazaar: Musings on Linux and Open Source by an Accidental Revolutionary (abbreviated CatB) is an essay, and later a book, by Eric S. Raymond on software engineering methods, based on his observations of the Linux kernel development process and his experiences managing an open source project, fetchmail. It examines the struggle between top-down and bottom-up design. The essay was first presented by the author at the Linux Kongress on May 27, 1997 in Würzburg (Germany) and was published as part of the same‑titled book in 1999.
The illustration on the cover of the book is a 1913 painting by Liubov Popova titled Composition with Figures and belongs to the collection of the State Tretyakov Gallery.
The book was released under the Open Publication License v2.0 in 1999.