LocalTalk is a particular implementation of the physical layer of the AppleTalk networking system from Apple Computer. LocalTalk specifies a system of four-wire cabling, plugged into self-terminating transceivers, running the AppleTalk protocol stack, at a rate of 232,000 bits/s.

Networking was envisioned in the Macintosh during planning, so the Mac was given expensive multi-mode (RS-232/RS-422) capable serial ports. Originally released as "AppleTalk Personal Network", LocalTalk used shielded twisted-pair cable with 3-pin Mini-DIN connectors. Cables were daisy-chained from transceiver to transceiver. Each transceiver had two 3-pin Mini-DIN ports, and a cable to connect to the Mac's DB-9 serial connector. Later, when the Mac Plus introduced the 8-pin Mini-DIN serial connector, transceivers were updated as well.

With the release of the iMac the traditional Mac serial port — and thus LocalTalk — finally went out of usage, though LocalTalk-to-Ethernet bridges were introduced to allow legacy devices (especially laser printers) to function on newer networks.

A variation of LocalTalk, called PhoneNet, was introduced by Farallon. It used standard telephone wire with RJ-11 connectors connected to a PhoneNet transceiver, instead of the expensive shielded twisted-pair cable. Because it offered identical performance at a substantially lower cost, PhoneNet entirely supplanted LocalTalk wiring, and eventually Apple itself abandoned LocalTalk wiring and marketed PhoneNet as LocalTalk.