Myrmeciinae is a subfamily of the Formicidae, ants once found worldwide but now restricted to Australia and New Caledonia. This subfamily is one of several ant subfamilies which possess gamergates, female worker ants which are able to mate and reproduce, thus sustaining the colony after the loss of the queen. The Myrmeciinae subfamily was formerly composed of only one genus, Myrmecia, but the subfamily was redescribed by Ward & Brady in 2003 to include two tribes and four genera. An additional three genera, one form genus, and 9 species were described in 2006 from the Early Eocene of Denmark, Canada, and Washington. Subsequently an additional fossil genus was moved from the family Rhopalosomatidae in 2018, and a new genus was described in 2021.

A gamergate is a mated worker ant that can reproduce sexually, i.e., lay fertilized eggs that will develop as females. In the vast majority of ant species, workers are sterile and gamergates are restricted to taxa where the workers have a functional sperm reservoir ('spermatheca'). In some species, gamergates reproduce in addition to winged queens, while in other species the queen caste has been completely replaced by gamergates. In gamergate species, all workers in a colony have similar reproductive potentials, but as a result of physical interactions, a dominance hierarchy is formed and only one or a few top-ranking workers can mate and produce eggs. Subsequently, however, aggression is no longer needed as gamergates secrete chemical signals that inform the other workers of their reproductive status in the colony.