Formicium is an extinct collective genus of giant ants in the Formicidae subfamily Formiciinae.

[1] The collective genus Formicium was first established by English entomologist and archaeologist John O. Westwood in 1854.

[3] When initially described by Theodore D. A. Cockerell, Formicium mirabilis was placed in the monotypic genus Megapterites.

This placement was retained in the Treatise on Invertebrate Paleontology Hymenoptera section written by Frank Carpenter.

[5] It has a long and narrow stigma (small, colored thick area near the wing-tip), and the discoidal cell is triangular.

The wings have similar dimensions to Dinomyrmex gigas, a giant ant found in Southeast Asia .