eMule is a free peer-to-peer file sharing application for Microsoft Windows. Started in May 2002 as an alternative to eDonkey2000, eMule connects to both the eDonkey network and the Kad network. The distinguishing features of eMule are the direct exchange of sources between client nodes, recovery of corrupted downloads, and the use of a credit system to reward frequent uploaders. eMule transmits data in zlib-compressed form to save bandwidth.

eMule is written in C++ using the Microsoft Foundation Classes. Since July 2002 eMule has been free software, released under the GNU General Public License; which has led to eMule's codebase being used as the basis of cross-platform clients aMule, JMule, xMule, along with the release of eMule modifications of the original eMule.

As of October 2023,^[update] it is the fifth most downloaded project on SourceForge, with over 693 million downloads.

Development was later restarted by the community as eMule Community.

The eMule project was started on May 13, 2002 by Hendrik Breitkreuz (also known as Merkur) who was dissatisfied with the original eDonkey2000 client. Over time more developers joined the effort. The source was first released at version 0.02 and published on SourceForge on July 6, 2002.

eMule was first released as a binary on August 4, 2002 at version 0.05a. The 'Credit System' was implemented for the first time on September 14, 2002 in version 0.19a. The eMule project website started up on December 8, 2002.

Versions v0.40+ of eMule added support for the Kad network. This network has an implementation of the Kademlia protocol, which does not rely on central servers as the eDonkey network does, but is an implementation of a distributed hash table.^{[citation needed]}

Also added was the ability to search using unicode, allowing for searches for files in non-Latin alphabets, and the ability to search servers for files with complete sources of unfinished files on the eDonkey network.^{[citation needed]}