The Bogdanov affair was an academic dispute regarding the legitimacy of obtaining Ph.D. degrees by French twins Igor and Grichka Bogdanov and a series of theoretical physics papers written by them in order to obtain degrees. The papers were published in reputable scientific journals, and were alleged by their authors to culminate in a theory for describing what occurred before and at the Big Bang.

Igor Youriévitch Bogdanoff and Grégoire "Grichka" Youriévitch Bogdanoff, alternatively spelled Bogdanov, were French twin television presenters, producers, and essayists who presented a variety of programmes in science fiction, popular science, and cosmology. They were involved in a number of controversies. The most notable is the Bogdanov affair. It brought to light how they received a Ph.D. degrees based of largely nonsensical physics papers that were nonetheless peer-reviewed and published in reputable scientific journals. In their later years, they were also the subject of numerous internet memes, particularly in the cryptocurrency community.