Alatheus (Jordanes' latinized form of a Gothic name, possibly Alaþius, was a Greuthung chieftain and general. He fought during the Hunnish invasion of 376, engaged in war with Rome from 376 to 383, and incursions into the Balkans in 387. He is most famous for his participation at the Battle of Adrianople in 378.
After the death of the Gothic King Vithimiris while fighting against the Huns in 376, Alatheus became, with Saphrax, coregent and guardian of Vithericus, infant son of Vithimiris. He helped in the leadership of the great Goth migration before the Hun onslaught, he crossed the Danube while Rome was busy with Therving refugees in that year. He soon allied himself with the Thervingian leaders Fritigern and Alavivus against Rome.
Alatheus eluded the Romans and rampaged through Thrace and Moesia in 377–378. He marched to Fritigern's aid against the Emperor Valens in the battle of Adrianople in 378, in which Valens was killed when the Alatheus' forces were victorious. He continued to raid Thrace and northern Greece, but was defeated by Theodosius the Great's general Promotus, and he settled on the north side of the Danube. He appeared on its banks again in 386, with the intention of invading the Roman provinces again. His forces were, however, repulsed, and Alatheus was slain.