Ustica is a small Italian island in the Tyrrhenian Sea. It is about 5 kilometres (3 mi) across and is situated 52 kilometres (32 mi) north of Capo Gallo, Sicily. Roughly 1,300 people live in the comune (municipality) of the same name. There is a regular ferry service from the island to Palermo in Sicily.

Amadeo Bordiga was an Italian Marxist theorist, revolutionary socialist, founder of the Communist Party of Italy (PCI), member of the Communist International (Comintern) and later a leading figure of the International Communist Party. Bordiga was originally associated with the PCI, but he was expelled in 1930 after being accused of Trotskyism.