Gnaeus Domitius Ahenobarbus (died 104 BC) was consul of Rome in 122 BC. He was the son of the Gnaeus Domitius Ahenobarbus who was consul in 162 BC.
In the year of his consulship he was sent against the Allobroges in Gallia Transalpina, under the pretext that they had received Rome's enemy, Teutomalius, king of the Salluvii, and had laid waste to the territory of Rome's allies, the Aedui. Rome’s desire to create a secure land route to their provinces in Spain through Gaul was more likely its real reason for entering Gaul. He and Quintus Fabius Maximus Allobrogicus conquered the Allobroges and their ally, Bituitus, king of the Arverni, near Vindalium, at the confluence of the Sulga and Rhone, winning the battle mainly through terror caused by war elephants. He erected trophies to commemorate his victory, traveled on an elephant in procession through the province, and was honored with a triumph in 120 BC, at the fore of which he paraded the captive Vituitus.
As censor in 115 BC, he expelled thirty-two senators from the senate. He is most famous for constructing the Via Domitia (cir. 118 BC), connecting Rome to her provinces in Spain. Constructed along an ancient trading road, crossing the Alps by one of the easiest passages, the Col de Montgenèvre., it is possibly the same pass taken by Hannibal in his famous crossing in 218 BC. It was built around the same time as the founding of Colonia Narbo Martius (Narbonne), the first Roman colony in Gaul.
He was also elected Pontifex.
He died around 104 BC.
He was surviled by at two sons, Gnaeus Domitius Ahenobarbus (consul in 96 BC) and Lucius Domitius Ahenobarbus (consul in 94 BC). He was the grandfather of Lucius Domitius Ahenobarbus (consul in 54 BC).