Pseudohistory is a form of pseudoscholarship that attempts to distort or misrepresent the historical record, often by employing methods resembling those used in scholarly historical research. The related term cryptohistory is applied to pseudohistory derived from the superstitions intrinsic to occultism. Pseudohistory is related to pseudoscience and pseudoarchaeology, and usage of the terms may occasionally overlap. Although pseudohistory comes in many forms, scholars have identified many features that tend to be common in pseudohistorical works; one example is that the use of pseudohistory is almost always motivated by a contemporary political, religious, or personal agenda. Pseudohistory also frequently presents sensational claims or a big lie about historical facts which would require unwarranted revision of the historical record.

A common feature of pseudohistory is an underlying premise that there is a conspiracy among scholars to promote so-called "mainstream history" over "true" history, an assertion commonly corroborated by elaborate conspiracy theories. Works of pseudohistory often point exclusively to unreliable sources—including myths and legends, often treated as literal historical truth—to support the thesis being promoted while ignoring valid sources that contradict it. Sometimes a work of pseudohistory will adopt a position of historical relativism, insisting that there is really no such thing as historical truth and that any hypothesis is just as good as any other. Many works of pseudohistory conflate mere possibility with actuality, assuming that if something could have happened, then it did.

Notable examples of pseudohistory include British Israelism, the Lost Cause of the Confederacy, the Irish slaves myth, the witch-cult, Armenian genocide denial, Holocaust denial, the clean Wehrmacht myth, the 16th- and 17th-century Spanish Black Legend, and the claim that the Katyn massacre was not committed by the Soviet NKVD.