Revisionist history was the practice of re-writing one's own history in order to support the narrative one wished to convey.
In 2368, Gowron rewrote Klingon history by claiming that it was his courage and genius which brought an end to the Klingon Civil War, and omitted all mention of the Federation's help in his rise to power. (TNG: "Unification I")
Around 3074, a backup of The Doctor criticized the Kyrians for portraying themselves as martyrs, heroes and saviors, while painting the crew of USS Voyager as the villains in an encounter with the ship seven hundred years earlier. He suggested that their motivation was to make themselves feel morally superior, adding, "Revisionist history. It's such a comfort." (VOY: "Living Witness")