Ethernet is a packet-based computer networking technology for local area networks (LANs). It defines wiring and signaling for the physical layer, and packet formats and protocols for the media access control (MAC)/data link layer of the OSI model. Ethernet is mostly standardized as IEEE's 802.3. It has become the most widespread LAN technology in use during the 1990s to the present (2004), and has largely replaced all other LAN standards such as token ring, FDDI, and ARCNET.

Ethernet was originally developed as one of the many pioneering projects at Xerox PARC. A common story states that Ethernet was invented in 1973, when Robert Metcalfe wrote a memo to his bosses at PARC about Ethernet's potential. Metcalfe claims Ethernet was actually invented over a period of several years. In 1976, Metcalfe and David Boggs (Metcalfe's assistant) published a paper titled, Ethernet: Distributed Packet-Switching For Local Computer Networks