In science fiction, mecha or mechs are giant robots or machines typically depicted as piloted and as humanoid walking vehicles. The term was first used in Japanese after shortening the English loanword 'mechanism' or 'mechanical' , but the meaning in Japanese is more inclusive, and 'robot' or 'giant robot' is the narrower term.

A walking vehicle is a vehicle that moves on legs rather than wheels or tracks. Walking vehicles have been constructed with anywhere from one to more than eight legs. There are many designs for the leg mechanisms of walking machines that provide foot trajectories with different properties.