Formica incerta is a species of ant found in eastern North America. It is the most common species of Formica in many areas and excavates underground nests with small entrance holes. Its diet includes nectar produced by extrafloral nectaries and honeydew which it obtains from aphids and treehoppers. It is the main host for the slave-making ant Polyergus lucidus. Formica incerta was first described by the Italian entomologist Carlo Emery in 1893. Its specific name comes from the Latin incertus meaning "uncertain" and seems particularly apt given the subsequent uncertainty as to the validity of the species and the difficulty in distinguishing this ant from other species living in the same area.