In the first millennium BCE, the Italian peninsula was home to a great variety of languages, some closely related and others very different. All these languages—except Greek, which had become established in southern Italy—were eventually replaced by the Latin that was spoken in Rome at the end of that millennium or the beginning of the Christian era. This chapter examines the stages, causes, and forms of the Latinization of Italy and the methods that allow for its study, focusing on particularly instructive case studies such as the self-Romanization of the elites, bilingualism, Gallia Cisalpina, Latin dialects, Faliscan, and the Sabellian languages.