GNU lightning is a library written in C for UNIX systems. It allows assembly language for a generic (and nonexistant) RISC chip architecture to be translated into machine code native to whatever architecture it is being run on. This allows programs to mix the best of assembly language (raw speed and the macho factor) with the portability of a higher-level laguage. It is useful for Just In Time compilers, such as the Java Virtual Machine.

It was written for UNIX (more specifically, GNU), but it will compile and run excellently on Cygwin. Currently it only has stable support for the x86 architecture, with support for SPARC and PowerPC being considered experimental.