Ariovistus was a leader of the Suebi and other allied Germanic peoples in the second quarter of the 1st century BC. He and his followers took part in a war in Gaul, assisting the Arverni and Sequani in defeating their rivals, the Aedui. Then, they settled in large numbers into conquered Gallic territory, in the Alsace region. They were defeated, however, in the Battle of Vosges and driven back over the Rhine in 58 BC by Julius Caesar.
Ariovistus and the events he was part of are known from Caesar's Commentarii de Bello Gallico. Caesar, as a participant in the events, is a primary source, but as his Commentaries were partly political, they may be suspected of being self-serving. Later historians, notably Dio Cassius, are suspicious of his motives.
Ariovistus was a native of the Suebi. He spoke Gaulish fluently. He had two wives, one of whom he had brought from home. The second, who was the sister of King Vocion of Noricum, he acquired in an arranged political marriage.
Ariovistus is described by Caesar as rex Germanorum. That is often translated as "king of the Germans", but as Latin had no definite article, it could equally be translated as "king of Germans", with no implication that he ruled all Germans. Indeed, Germania is known to have been divided into many tribal and political groups, many of which were ruled by kings. It is likely that Ariovistus's authority extended only over those Germans who had settled in Gaul.
He was recognised as a king by the Roman Senate, but how closely the Roman title matched Ariovistus's social status among the Germans remains unknown. Similarly, what the senate meant by rex at that moment in the history of the Roman Republic is not clear. The word "king" can have many meanings and did so throughout Rome's centuries of history. Tacitus says that the Germans made a distinction between kings, who were chosen by birth, and military leaders, who were chosen by ability, and that kings did not have absolute power.