Thief ants are a group of ants within the genus Solenopsis that make their living by constructing a nest next to the nests of other ants. They then tunnel into the nest of the neighboring ants and make their way to the brood chambers where larvae, pupae, and eggs are kept. Once there, the thief ant foragers live up to their name by carrying off the eggs and brood of their hosts. The stolen brood becomes the food of the thief ants. Some thief ants (those in the S. molesta species group) may also occasionally become household pests, living in nests constructed in cracks, under floors, and behind baseboards from which they forage on greasy scraps that they find in the house.

Thief ants are able to effectively steal the brood of their hosts and retreat to their own burrows for several reasons. First, they are extremely small. The tunnels that they use to infiltrate the host nests are small enough that the host defenders cannot persue them. Second, these ants are ferocious fighters with strong mandibles and a nasty sting. Finally, the venom of thief ants is, itself, a powerful ant repellent and the theif ants use it to make the portions of the host ant's nest that they invade noxious to the hosts.