Usera Tunnel was a scam operated by Republican security units during the Spanish Civil War. It took place in Madrid between mid-October and mid-November 1937. Its objectives were twofold; one was to capture supposed supporters of the Nationalists, who were hiding in Madrid, mostly in premises of foreign diplomatic missions; another was to enrich the scammers by robbing the victims of money and valuables. The scammers floated rumors about an underground tunnel, allegedly located in the Madrid suburb of Usera and running below the frontline to the Nationalist-held sector. Posing as corrupted Republican militiamen they lured at least 67 individuals, who were imprisoned, robbed and killed in army premises near the frontline. Three individuals charged with operating the scam were later apprehended and executed in the Francoist Spain; one more died in prison. Casimiro Duran Muñoz, the officer deemed to have been the chief engineer of the project, was last seen in 1938 and his later fate is unknown.

Usera is a district of Madrid, Spain. It lies on the southern (right) bank of the Manzanares. It is home to about a 10% of the Chinese citizens in the whole Madrid region.