Message Passing Interface (MPI) is a standardized and portable message-passing standard designed to function on parallel computing architectures.

MPI (Message Passing Interface) is the *de facto* standard paradigm for programming computational systems with distributed memory. It is an open specification that replaces various incompatible vendor communication interfaces and so ensures source code portability to various distributed memory platforms. The MPI specification is being maintained and further developed by the ​MPI Forum​, a not-for-profit organisation whose members are various HPC users, software and hardware vendors. The text of the specification can be downloaded for free from the web site of the forum or ordered in book form for the price of printing the copy. MPI is a language- and platform-neutral set of primitives for data exchange and parallel I/O. It also includes two standard language bindings (concrete specifications of how each primitive should be invoked in a given language) for C and Fortran.