Not every conspiracy theory is false—and not every official account is complete. The historical record contains genuine conspiracies: documented, prosecuted, and proven through evidence. It also contains an enormous body of unfounded belief that has shaped political movements, destabilized democracies, and occasionally incited violence. Conspiracies Decoded draws a rigorous line between these categories, examining both the real conspiracies that history has confirmed and the mythologies that flourished in their shadow. Drawing on declassified government documents, court records, investigative archives, and the scholarship of historians and psychologists, each chapter examines a distinct case—from the verified conspiracies of the Cold War era, Watergate, and COINTELPRO, to the elaborately constructed fictions of QAnon, moon landing denial, and New World Order mythology. The book does not treat believers with contempt. Instead, it asks the more historically productive question: what conditions—institutional distrust, information asymmetry, political trauma—make populations receptive to conspiratorial thinking, and what does the historical record actually show when primary sources are examined directly? The final section traces the evolution of conspiracy culture through the digital age, examining how social media algorithms, political polarization, and declining institutional credibility have transformed fringe belief into mainstream political currency. Conspiracies Decoded is neither a debunking exercise nor a validation of suspicion—it is a serious historical inquiry into the boundary between legitimate skepticism and documented reality, written for readers who believe that evidence, carefully examined, remains the most powerful tool available.