Apologia Pro Vita Sua (transl. 'A defence of one's own life') is John Henry Newman's history of his religious opinions, showing how his opinions had been formed and how they had led him from Anglicanism to the Catholic Church. It was originally published as a series of pamphlets in 1864 in response to an attack by Charles Kingsley against Newman's honesty. Though Newman's honesty had been widely questioned for years, the Apologia was immensely successful and cleared Newman's name. Newman published a revised version in 1865.

Between the publication of Tract 90 in 1841 and his conversion to Catholicism in 1845, Newman had been accused of secretly working to convert people to Catholicism while outwardly professing to be Anglican, and the belief in his dishonesty during that period persisted even into the 1860s. Newman's reputation in the early 1860s was at a low point, and he was seen as a "safe object" for insult and ridicule. He had refrained from answering the attacks because of their anonymity or because they had been only short gibes; however, he had decided that if someone more well-known were to make an extended and public attack against him, he would defend himself.

In the January 1864 issue of Macmillan's Magazine, Charles Kingsley, in a review of James Anthony Froude's History of England, remarked: "Truth, for its own sake, had never been a virtue with the Roman clergy. Father Newman informs us that it need not, and on the whole ought not to be." Newman received a copy of the issue on 30 December 1863; not knowing who had written the review, he wrote to the publisher noting that the accusation had not been substantiated by any evidence. Kingsley replied, justifying his comment by pointing to a sermon Newman had given in 1844, though without giving a specific passage.

Newman answered that the sermon in question had been given while he was yet Anglican, and moreover contained no such claim about the truthfulness of Catholic priests. Kingsley wrote an apology which he offered to publish, but Newman objected that, as written, it implied that Newman had explained an offending passage, while Newman contended that he had never been provided with a passage from his writings to explain. Kingsley revised the apology, and, though Newman was still dissatisfied, published it in the February issue of Macmillan's Magazine.

In response, Newman published a pamphlet on 12 February containing the correspondence between himself and Kingsley along with some "reflections", including a sarcastic summary of the correspondence. On 20 February, Richard Holt Hutton, editor of The Spectator, published a review of the pamphlet and summary of the controversy, concluding that Newman was in the right, though had perhaps been too harsh. Hutton praised Newman's writing and intellect, calling him "the very greatest master of delicate and polished sarcasm in the English language", and claiming that Kingsley "drew down upon himself" Newman's response.

Though Newman had previously informed Kingsley that he considered Kingsley's letters public, which Kingsley readily acknowledged as his right, Kingsley was angered by the publishing of the correspondence, viewing it as a breach of etiquette. On 20 March, he published a pamphlet entitled What, Then, Does Dr. Newman Mean?, in which, though retracting the charge of "conscious dishonesty", he further attacked Newman's truthfulness. Hutton again took Newman's part and accused Kingsley of adding to the original offence, and there was a general feeling that Kingsley had gone too far. Newman, seeing that public opinion was in his favour, decided to take the opportunity for a fair hearing and publish a "history of [his] opinions".

Newman originally planned to deliver his response as a series of lectures, but decided that such a format would not be suitable for the personal history he intended. A complete book would also be unsuitable both because the length would deter readers and because by the time it was published, the controversy would have cooled and interest would have waned. Instead, Newman decided to publish a series of weekly pamphlets.

Newman had been sorting his papers and letters in view of someday needing to defend himself, but had only got to 1836. He asked old friends, including those from the Oxford Movement, to check his pamphlets for accuracy. He thought it providential that he had recently got back in touch with some of his Anglican friends, though he worried about asking for their help since his work would unintentionally portray Anglicanism in a negative light. However, Newman made an effort to portray both friends and enemies fairly, for which they were grateful.