The Riom Trial (; 19 February 1942 – 21 May 1943) was an attempt by the Vichy France regime, headed by Marshal Philippe Pétain, to prove that the leaders of the French Third Republic (1870–1940) had been responsible for France's defeat by Germany in 1940. The trial was held in the city of Riom in central France, and had mainly political aims – namely to project the responsibility of defeat onto the leaders of the left-wing Popular Front government that had been elected 3 May 1936.