M. exigua may refer to:
Madia exigua, a western North American plant Meloidogyne exigua, a coffee root-knot nematode Micromystix exigua, a snout moth Micropyxis exigua, a perennial herb Miresa exigua, a slug moth Mitromorpha exigua, a sea snail Mordellistena exigua, a tumbling flower beetle Mycosphaerella exigua, a plant pathogen Myrmecia exigua, a bulldog ant Myrmica exigua, an ant with a binodal petiole Myrmicaria exigua, an ant with an antenna with seven segments