Farnobius was the "optimatus" (or chieftain) of one of the Greuthungi tribes, who were pressing on the Danubian frontier during the 370s as a result of westward pressure by the Huns. In 376, with the outbreak of the Gothic War, Farnobius led his people across the Danube from Muntenia, and poured into Moesia Secunda, together with two other Greuthungi tribes, led by Alatheus and Saphrax. Soon however, Farnobius broke away from the coalition, and proceeded to operate independently from the rest of the Greuthungi.