DECnet is a suite of network protocols created by Digital Equipment Corporation. Originally released in 1975 in order to connect two PDP-11 minicomputers, it evolved into one of the first peer-to-peer network architectures, thus transforming DEC into a networking powerhouse in the 1980s. Initially built with three layers, it later (1982) evolved into a seven-layer OSI-compliant networking protocol.

DECnet was built right into the DEC flagship operating system OpenVMS since its inception. Later Digital ported it to Ultrix, as well as Apple Macintosh and IBM PC running variants of DOS and Microsoft Windows under the name DEC Pathworks, allowing these systems to connect to DECnet networks of VAX machines as terminal nodes.

While the DECnet protocols were designed entirely by Digital Equipment Corporation, DECnet Phase II (and later) were open standards with published specifications, and several implementations were developed outside DEC, including ones for FreeBSD and Linux. DECnet code in the Linux kernel was marked as orphaned on February 18, 2010.