Mus·so·li·ni (mōō'sə-lē'nē, mŏŏs'ə-, mōōs'sō-) Italian Fascist dictator and prime minister (1922-1943) who conducted an expansionist foreign policy, formalized an alliance with Germany (1939), and brought Italy into World War II (1940). Dismissed by Victor Emmanuel III (1943), he led a puppet Nazi government in northern Italy until 1945, when he was assassinated.