Furor Teutonicus ("Teutonic Fury") is a Latin phrase referring to the proverbial fierceness of the Teutones, or more generally the Germanic tribes of the Roman Empire period.
The original expression is generally attributed to the Roman poet Marcus Annaeus Lucanus, also known as Lucan. It occurs for the first time in his work Bellum civile/Pharsalia. Lucan used the term to describe what he believed to be the outstanding characteristic of the Germanic tribe called the Teutones: a mad, merciless, berserk rage in battle.
The Teutons met with the armies of the Roman Empire in the eastern Alps around 113 BC. The Romans, under the command of the Consul Papirius Carbo, tried to lure the tribe into a trap, but they underestimated their military potential and lost the Battle of Noreia. The Romans also lost the Battle of Arausio (105 BC) and other lesser battles, before putting Gaius Marius in charge of their defence.
The Teutons were defeated in 102 BC, but other Germanic tribes remained a worry for the Roman Empire until its conquest and destruction by Germanic mercenaries under the Germanic chieftain Odoacer. After the final defeat of the Roman Army at the Battle of the Teutoburg Forest and the complete annihilation of three Roman legions (between 20,000 and 30,000 men), Rome never again tried to conquer Germania.