Unione Sindacale Italiana (USI; Italian Syndicalist Union or Italian Workers Union) is an anarcho-syndicalist trade union. It is the Italian section of the International Workers Association (IWA; Associazione Internazionale dei Lavoratori in Italian or AIT - ''Asociación Internacional de los Trabajadores in the common Spanish reference), and the name of USI is also abbreviated as USI-AIT.
Read more about Unione Sindacale Italiana: Early History, The Fascist Regime and Afterwards, Split in USI