In historiography, historical revisionism is the reinterpretation of a historical account. It usually involves challenging the orthodox (established, accepted or traditional) views held by professional scholars about a historical event or timespan or phenomenon, introducing contrary evidence, or reinterpreting the motivations and decisions of the people involved. The revision of the historical record can reflect new discoveries of fact, evidence, and interpretation, which then results in revised history. In dramatic cases, revisionism involves a reversal of older moral judgments.

At a basic level, legitimate historical revisionism is a common and not especially controversial process of developing and refining the writing of histories. Much more controversial is the reversal of moral findings, whereby what mainstream historians had considered (for example) positive forces are depicted as negative. Such revisionism, if challenged (especially in heated terms) by the supporters of the previous view, can become an illegitimate form of historical revisionism known as historical negationism if it involves inappropriate methods such as the use of forged documents or implausible distrust of genuine documents, attributing false conclusions to books and sources, manipulating statistical data, and deliberately mistranslating texts. This type of historical revisionism can present a re-interpretation of the moral meaning of the historical record. Negationists use the term revisionism to portray their efforts as legitimate historical inquiry; this is especially the case when revisionism relates to Holocaust denial.