Gnaeus Domitius Ahenobarbus (11 December 17 BC - January 40 AD) was a close relative to the Roman Emperors of the Julio-Claudian dynasty.

Domitius was the only son to Antonia Major and Lucius Domitius Ahenobarbus. Antonia was daughter to Marcus Antonius and Octavia, sister of Roman Emperor Caesar Augustus.

Domitius' maternal aunts included Antonia Minor, Cleopatra Selene, Claudia Marcella Major, Claudia Marcella Minor. His maternal uncles included Iullus Antonius, Alexander Helios and Ptolemy Philadelphus and Marcellus.

Domitius was thus first cousin to among others Germanicus, Livilla, Claudius, Ptolemy of Mauretania, Drusilla of Mauretania, Claudia Pulchra and Marcus Valerius Messalla Barbatus.

Domitius was also first cousin, once removed, to their children. A group including among others Julia Livilla, Drusilla, Agrippina the younger, Drusus Caesar, Nero Caesar, Caligula, Claudia Julia, Tiberius Gemellus, Britannicus, a younger Octavia, allegedly Julia Venissa and Messalina.

Domitius' sister Domitia Lepida was also mother to the previously mentioned Messalina.

Domitius was thus related to several notable figures who would dominate the Roman Empire during the 1st century. Suetonius describes him as ‘despicable and dishonest’. As a young man, Domitius was serving on the staff of his second cousin Gaius Caesar in the East. Gaius was son of Marcus Vipsanius Agrippa and Julia Caesaris, daughter to the previously mentioned Caesar Augustus. Domitius fortified their friendship by killing his freedman. The reported reason was that the freedman did not get as drunk as Domitius did. On the Appian Way, Domitius was reported of having deliberately ran over a child (who was playing) with his horses . At the Roman Forum Domitius reportedly pulled out an eye of a knight because the knight openly criticized him.

Domitius cheated on bankers, for purchases he made. When Praetor, Domitius would swindle the prize money of victorious charioteers. Managers would complain, but Domitius decreed that future prizes would be paid on the spot. Tiberius charged him with treason, adultery and incest with his sister but the ascension of Caligula saved him. Domitius was also considered a serious womanizer.

Domitius married his cousin Julia Agrippina after her thirteenth birthday in 28 AD. Tiberius arranged and ordered the marriage which was celebrated at the Capital, Rome. Domitius was wealthy but apparently chose to live between Antium and Rome.

Domitius was Consul in 32 AD and appointed by Tiberius as a commissioner in early 37 AD.

His son Lucius Domitius Ahenobarbus (Nero) was born on 15 December 37 AD in Antium. He died of dropsy at Pyrgi in January, 40 AD. In Domitius' will Lucius inherited 1/3 of his estate. But Caligula, who was also mentioned in the will, took Lucius' inheritance for himself. When Claudius became Emperor, Lucius' inheritance was restored.

Domitius' widow Agrippina later married her widowed uncle Claudius. Lucius was adopted by the elderly Emperor as "Nero Claudius Caesar Drusus". When Claudius died on October 13, 54, Lucius succeeded him as "Nero Claudius Caesar Augustus Germanicus". Nero exalted Domitius’ memory and the Roman Senate arranged for the construction of his statue in 55 AD.