VAXELN (typically pronounced "VAX-elan") is a discontinued real-time operating system for the VAX family of computers produced by the Digital Equipment Corporation (DEC) of Maynard, Massachusetts.

As with RSX-11 and VMS, Dave Cutler was the principal force behind the development of this operating system. Cutler's team developed the product after moving to the Seattle, Washington area to form the DECwest Engineering Group; DEC's first engineering group outside New England. Initial target platforms for VAXELN were the backplane interconnect computers such as the model code-named Scorpio. When VAXELN was well under way, Cutler spearheaded the next project, the MicroVAX I, the first VAX microcomputer. Although it was a low-volume product compared with the New England-developed MicroVAX II, the MicroVAX I demonstrated the set of architectural decisions needed to support a single-board implementation of the VAX computer family, and it also provided a platform for embedded system applications written for VAXELN.

The VAXELN team made the decision, for the first release, to use the programming language Pascal as its system programming language. The development team built the first product in approximately 18 months. Other languages, including C, Ada, and Fortran were supported in later releases of the system as optional extras. A relational database, named VAX Rdb/ELN was another optional component of the system. Later versions of VAXELN supported an X11 server named EWS (VAXELN Window Server). VAXELN with EWS was used as the operating system for the VT1300 X terminal, and was sometimes used to convert old VAXstation hardware into X terminals. Beginning with version 4.3, VAXELN gained support for TCP/IP networking and a subset of POSIX APIs.

VAXELN allowed the creation of a self-contained embedded system application that would run on VAX (and later MicroVAX) hardware with no other operating system present. The system was debuted in Las Vegas in the early 1980s, with a variety of amusing application software written by the development team, ranging from a system that composed and played minuets to a robotic system that played and solved the Tower of Hanoi puzzle.

VAXELN was not ported to the DEC Alpha architecture, and instead was replaced with a Digital-supported port of VxWorks to Alpha, and a VAXELN application programming interface (API) compatibility layer for that platform. In 1999, SMART Modular Technologies acquired Compaq's (formerly Digital's) embedded systems division, which included VAXELN.