An OUT file is a compiled executable file created by various source code compilers in Unix-like operating systems, such as Linux and AIX. It may store executable code, shared libraries, or object code. OUT files have been largely replaced by the newer COFF (Common Object File Format) format.

OUT files are most commonly seen as a.out files. The name stands for "assembler output" and is a format used by the PDP-7 and PDP-11 series of minicomputers. The "a.out" filename may also be given to OUT files not saved in the "assembler output" format but instead is just the default name given to output files when no name is applied.