Ophiocordyceps formicarum is an entomopathogenic fungus belonging to the order Hypocreales (Ascomycota) in the family Ophiocordycipitaceae.

The fungus was first described by mycologist George S. Kobayashi in 1939 as a species of Cordyceps.

Originally found in Japan growing on an adult Hercules ant (Camponotus herculeanus var.

[3] It was transferred to the new genus Ophiocordyceps in 2007 when the family Cordycipitaceae was reorganized.

[1] A technique has been developed to grow the fungus in an agar growth medium supplemented with yeast extract, inosine, and glucose.