Project Gutenberg, abbreviated as PG, is a volunteer effort to digitize and archive cultural works, to "encourage the creation and distribution of eBooks." Founded in 1971 by Michael S. Hart, it is the oldest digital library. Most of the items in its collection are the full texts of public domain books. The project tries to make these as free as possible, in long-lasting, open formats that can be used on almost any computer. As of March 2009, Project Gutenberg claimed over 28,000 items in its collection. Project Gutenberg is affiliated with many projects that are independent organizations which share the same ideals, and have been given permission to use the Project Gutenberg trademark (from Project_Gutenberg).

Project Gutenberg was started by Michael Hart in 1971 with the digitization of the United States Declaration of Independence. Hart, a student at the University of Illinois, obtained access to a Xerox Sigma V mainframe computer in the university's Materials Research Lab. Through friendly operators, he received an account with a virtually unlimited amount of computer time; its value at that time has since been variously estimated at $100,000 or $100,000,000.4 Hart has said he wanted to "give back" this gift by doing something that could be considered to be of great value. His initial goal was to make the 10,000 most consulted books available to the public at little or no charge, and to do so by the end of the 20th century.