Wikisource is an online digital library of free content textual sources on a wiki, operated by the Wikimedia Foundation. Its aims are to host all forms of free text, in many languages, and translations. Originally conceived as an archive to store useful or important historical texts, it has expanded to become a general-content library. The project officially began in November 24, 2003 under the name Project Sourceberg. The name Wikisource was adopted later that year and it received its own domain name seven months later. The project has come under criticism for lack of reliability but it is also cited by organisations such as the National Archives and Records Administration.

The project holds works that are either in the public domain or freely licenced; professionally published works or historical source documents, not vanity products; and are verifiable. Verification was initially made offline, or by trusting the reliability of other digital libraries. Now works are supported by online scans via the ProofReadPage extension, which ensures the reliability and accuracy of the project's texts. Some Wikisources now only allow works backed up with scans. While the bulk of its collection are texts, Wikisource hosts other media, from comics to film to audio books. The only original works allowed on Wikisource are translations and annotations.