Lasius Latr. is a genus of boreal formicine ants.

Included within this genus is the common black garden ant, Lasius niger, and its close relative from dry heathland, L. alienus.

Other species include the temporary social parasites of the L. mixtus group and the hyper-social parasite Lasius fuliginosus.

Lasius flavus is also a commonly seen species, building grassy hillocks in undisturbed pasture. In the alps these mounds - always aligned east to catch the first rays of the rising sun - have been traditionally used by goatherds as natural compasses.

The genus was renamed by Horace St. John Kelly Donisthorpe, the eccentric British myrmecologist and coleopterist, after himself Donisthorpea

Synonyms: Donisthorpea Donisthorpe