The gens Aelia, occasionally written Ailia, or Ælia, was a plebeian family in Rome, which flourished from the fifth century BC until at least the third century AD, a period of nearly eight hundred years. The archaic spelling Ailia is found on coins, but must not be confused with Allia, which is a distinct gens. The first member of the family to obtain the consulship was Publius Aelius Paetus in 337 BC.
Under the empire the Aelian name became still more celebrated. It was the name of the emperor Hadrian, and consequently of the Antonines, whom he adopted. A number of landmarks built by Hadrian also bear the name Aelius. The Pons Aelius is a bridge in Rome, now known as the Ponte Sant'Angelo. Pons Aelius also refers to a Roman settlement in Britannia Inferior, now the site of Newcastle upon Tyne, while Aelia Capitolina was a Roman colony built on the ruins of Jerusalem.
The Aelii regularly used the praenomina Publius, Sextus, Quintus, and Lucius. There is also one example of Gaius amongst the early members of the gens.
The family-names and surnames of the Aelia gens are Catus, Gallus, Gracilis, Lamia, Ligur, Paetus, Staienus, Stilo, and Tubero. The only cognomina found on coins are Bala, Lamia, Paetus, and Sejanus. Of Bala nothing is known. Sejanus is the name of the favorite of the emperor Tiberius, who was adopted by one of the Aelii.