The BBN Butterfly was a massively parallel computer from the 1980s based on an earlier Pluribus design. It was named for the "butterfly" multi-stage switching network around which it was built. Each machine had to 512 CPUs, each with local memory, which could be connected to allow every CPU access to every other CPU's memory, although with a substantially greater latency (roughly 15:1) than for its own. The CPUs were commodity microprocessors. The earlier, GP-1000 models used Motorola 68020's and scaled to 256 CPUs. The later, TC-2000 models used Motorola 88100 's, and scaled to 512 CPUs.

The Butterfly began with a proprietary operating system called Chrysalis, but moved to a Mach kernel operating system in 1989. While the memory access time was non-uniform, the machine had SMP memory semantics, and could be operated as a symmetric multiprocessor.

TotalView[tm], the parallel program debugger developed for the Butterfly outlived the platform, to be ported to a number of other massively parallel machines.