MPICH, formerly known as MPICH2, is a freely available, portable implementation of MPI, a standard for message-passing for distributed-memory applications used in parallel computing.

MPICH is Free and open source software with some public domain components that were developed by a US governmental organisation,[2] and is available for most flavours of Unix-like OS (including Linux and Mac OS X).

The Argonne National Laboratory and Mississippi State University jointly developed early versions (MPICH-1) as public domain software.

The CH part of the name was derived from "Chameleon", which was a portable parallel programming library developed by William Gropp, one of the founders of MPICH.

As of November 2012, the MPICH2 project renamed itself to simply "MPICH".