A special ops unit founded by Big Boss in 1971. Its members are given a FOXHOUND codename. The group was founded when its precursor, FOX, went renegade, and a new unit was created in order to eliminated it—thus its name. In keeping with FOX, its primary function is to carry out one-man infiltration missions, procuring all weaponry in the field, and leaving no trace of its presence.

The unit's first commander was the Legendary Mercenary, Big Boss; its second, Roy Campbell. FOXHOUND was highly regarded after its successful one-man infiltration missions during the upheavals in Outer Heaven and Zanzibarland. The FOXHOUND emblem in use at this time was comical in design.

In 2005, an active unit of FOXHOUND went renegade on the island of Shadow Moses, a situation which came to be called the Shadow Moses Incident. An ex-member of FOXHOUND, Solid Snake, quelled the rebellion, and the unit was disbanded.

FOXHOUND has not been reinstated since the Shadow Moses Incident. The so-called FOXHOUND that Raiden believed himself a member of only "existed" as digital data, a virtual unit created by the Patriots.