The Affair of the Placards was an incident involving anti-Catholic posters which appeared in public places in Paris, France during the night of October 18, 1534. It marks the end of the conciliatory policies of Francis I, who had formerly attempted to protect the Protestants from the more extreme measures of the French Parlement.

The author of the placards is not known; but traditionally, the French Protestant leader Guillaume Farel is thought to have been the chief inspiration, if not the direct author of the papers. They were an open attack on the Mass, the central ritual of the Roman Catholic Church, entitled "True articles on the horrible, great and insufferable abuses of the papal mass". The polemic against the Catholic church was an embarrassment to the pro-reform Catholics, and the immediate public outcry necessitated the flight of several prominent Protestant leaders, including John Calvin.