In science fiction, mecha (Japanese: メカ) or mechs are giant robots or machines typically depicted as piloted and as humanoid walking vehicles.

Fictional mecha vary greatly in size and shape, but are distinguished from vehicles by their humanoid or biomorphic appearance, although they are bigger, often much bigger, than human beings. Different subgenres exist, with varying connotations of realism. The concept of Super Robot and Real Robot are two such examples found in Japanese anime and manga.