I, Claudius is a historical novel written by Robert Graves and published in 1934. Written in the form of an autobiography of the Roman Emperor Claudius, it tells the history of the Julio-Claudian dynasty and the early years of the Roman Empire, from Julius Caesar's assassination in 44 BC to Caligula's assassination in AD 41. Though the narrative is largely fictionalised, most of the events depicted are drawn from historical accounts of the same time period by the Roman historians Suetonius and Tacitus.

The "autobiography" continues in a sequel, Claudius the God (1935), which covers the period from Claudius' accession to his death in AD 54. The sequel also includes a section written as a biography of Herod Agrippa, a contemporary of Claudius and the king of Judaea (Roman province). Both books were adapted by the BBC into the award-winning television serial I, Claudius in 1976.

Graves stated in an interview with Malcolm Muggeridge in 1965, that he wrote I, Claudius mainly because he needed the money to pay off a debt, having been let down in a land deal. He needed to raise £4,000 (equivalent to £359,000 in 2023), but with the success of the books he brought in £8,000 (£701,000) in six months, thus extricating himself from his precarious financial position.

In 1998, the Modern Library ranked I, Claudius fourteenth on its list of the 100 best English-language novels of the 20th century. In 2005, the novel was chosen by Time as one of the 100 best English-language novels from 1923 to present.

Claudius was the fourth Emperor of the Roman Empire, from AD 41 to 54. A grandson of Mark Antony and great-nephew of Augustus, he was a member of the Julio-Claudian family, Rome's first imperial ruling family. Claudius' family kept him out of public life until his sudden coronation at the age of fifty because of his persistent stammer, limp, and other nervous tics, which caused others to perceive him as mentally deficient and not a threat to his ambitious relatives. Even as his symptoms began to wane in his teenage years, he ran into trouble as a budding historian; his work on a history of the Roman civil wars was either too truthful or too critical of the reigning emperor Augustus, and his mother Antonia Minor and grandmother Livia quickly put a stop to it. This episode reinforced their initial suspicions that Claudius was not fit for public office.

Claudius was portrayed this way by scholars for most of history, and Graves uses these peculiarities to develop a sympathetic character whose survival in a murderous dynasty depends upon his family's incorrect assumption that he is a harmless idiot. Graves' interpretation of the story owes much to the histories of Gaius Cornelius Tacitus, Plutarch, and (especially) Suetonius' Lives of the Twelve Caesars. Graves translated Suetonius before writing the novels and claimed that after reading Suetonius, Claudius came to him in a dream one night and demanded that his real story be told. The life of Claudius provided Graves with a way to write about the first four emperors of Rome from an intimate point of view. I, Claudius is written as a first-person narrative of Roman history from Claudius' perspective, covering the reigns of Augustus, Tiberius, and Caligula; Claudius the God is written as a later addition documenting Claudius' own reign. The real Claudius was a trained historian and is known to have written an autobiography (now lost) in eight books that covered the same period.

Graves provides a theme for the story by having the fictional Claudius describe a visit to Cumae, where he receives a prophecy in verse from the Sibyl and an additional prophecy contained in a book of "Sibylline Curiosities". The latter concerns the fates of the "hairy ones" (i.e. the Caesars – from the Latin word "caesar", meaning "a fine head of hair") ^{[dubious – discuss]} who are to rule Rome. The penultimate verse concerns his reign and Claudius assumes that he can tell the identity of the last emperor described in the prophecy. Graves establishes a fatalistic tone that plays out at the end of Claudius the God when Claudius correctly predicts his assassination and succession by Nero.

At Cumae, the Sibyl tells Claudius that he will "speak clear". Claudius believes this means that his secret memoirs will one day be found and that he, having written the truth, will speak clearly, while his contemporaries, who had to distort their histories to appease the ruling family, will seem like stammerers. Since he wishes to record his life for posterity, Claudius explains that he chooses to write in Greek, which he believes will remain "the chief literary language of the world". This enables Graves' Claudius to offer explanations of Latin wordplay or etymologies that would seem unnecessary if his autobiography had been written for native Latin speakers. Claudius also portrays his grandmother Livia as a scheming Machiavellian, based on the works of Tacitus and Cassius Dio, who wrote that rumours persisted that Augustus was poisoned by Livia, but these are mainly dismissed as malicious fabrications spread by political enemies of the dynasty.