The gens Claudia (Latin: [ˈkɫau̯di.a]), sometimes written Clodia, was one of the most prominent patrician houses at ancient Rome. The gens traced its origin to the earliest days of the Roman Republic. The first of the Claudii to obtain the consulship was Appius Claudius Sabinus Regillensis, in 495 BC, and from that time its members frequently held the highest offices of the state, both under the Republic and in imperial times.

Plebeian Claudii are found fairly early in Rome's history. Some may have been descended from members of the family who had passed over to the plebeians, while others were probably the descendants of freedmen of the gens. In the later Republic, one of its patrician members voluntarily converted to plebeian status and adopted the spelling "Clodius".

In his life of the emperor Tiberius, who was a scion of the Claudii, the historian Suetonius gives a summary of the gens, and says, "as time went on it was honoured with twenty-eight consulships, five dictatorships, seven censorships, six triumphs, and two ovations." Writing several decades after the fall of the so-called "Julio-Claudian dynasty", Suetonius took care to mention both the good and wicked deeds attributed to members of the family.

The patrician Claudii were noted for their pride and arrogance, and intense hatred of the commonalty. In his History of Rome, Niebuhr writes,

That house during the course of centuries produced several very eminent, few great men; hardly a single noble-minded one. In all ages it distinguished itself alike by a spirit of haughty defiance, by disdain for the laws, and iron hardness of heart.

During the Republic, no patrician Claudius adopted a member of another gens; the emperor Claudius was the first who broke this custom, by adopting Lucius Domitius Ahenobarbus, afterwards the emperor Nero.

According to legend, the first of the Claudii was a Sabine, by the name of Attius Clausus, who came to Rome with his retainers in 504 BC, the sixth year of the Republic. At this time, the fledgling Republic was engaged in regular warfare with the Sabines, and Clausus is said to have been the leader of a faction seeking to end the conflict. When his efforts failed, he defected to the Romans, bringing with him no fewer than five hundred men able to bear arms, according to Dionysius.

Clausus, who exchanged his Sabine name for the Latin Appius Claudius, was enrolled among the patricians, and given a seat in the Senate, quickly becoming one of its most influential members. His descendants were granted a burial site at the foot of the Capitoline Hill, and his followers allotted land on the far side of the Anio, where they formed the core of what became the "Old Claudian" tribe.