The "Mithridates Letters" are a collection of fictional rhetorical exercises from the Roman imperial period, not the work of a single, known author. They were likely composed in the 1st or 2nd century CE as part of the Second Sophistic, a cultural movement that valued skilled oratory in classical Greek. The letters are written in the voice of Mithridates VI, the king of Pontus who fought three major wars against Rome in the 1st century BCE.

The work is a form of advanced school exercise, where the anonymous author invents persuasive speeches for a historical figure. The dramatic setting is the First Mithridatic War (89–85 BCE). In the letters, Mithridates addresses various kings and nations, urging them to form a coalition against Roman expansion. While the historical king did seek such alliances, the specific arguments and eloquent language of these texts are invented.

The single surviving work, sometimes called The Letter of Mithridates, has been preserved because it was transmitted as an appendix to the historical works of the Roman author Sallust. Modern scholars universally recognize it as a later, pseudonymous composition. According to modern scholars, its significance lies in demonstrating how Roman-era students practiced rhetoric. It used a famous enemy of Rome as a safe vehicle for crafting powerful anti-Roman arguments, providing insight into the era's historical imagination and educational practices.