The jack jumper ant (Myrmecia pilosula), also known as the jack jumper, jumping jack, hopper ant, or jumper ant, is a species of venomous ant native to Australia. Most frequently found in Tasmania and southeast mainland Australia, it is a member of the genus Myrmecia.

The jack jumper ant 7genome is contained on a single pair of chromosomes (males have just one chromosome, as they are haploid). This is the lowest number known (indeed possible) for any animal, a number shared with the parasitic roundworm Parascaris equorum univalens. Jack jumper ants are taxonomically discussed as a single biological species in the Myrmecia pilosula species complex. The ant has nine polymorphic loci, which yielded 67 alleles.