Language reflects social change. This is perhaps nowhere better illustrated than in Japan, where massive upheavals in the use of language have occurred over the past two hundred years. These changes have affected not only the Japanese language itself, but also Japanese attitudes to their own and other languages. Neither are these attitudes constant. They fluctuate over time, reflecting the prevailing political or social climate, or the views, whether progressive or conservative, of the protagonists in the language debate. As with other aspects of Japanese culture, the story of language in modern Japan reverberates with the tensions between the centripetal forces of standardisation, unity and nationalism on the one hand and the centrifugal imperatives of diversity, regional identity and internationalism on the other. This chapter aims to provide a broad overview of language in modern Japan, dealing not only with Japanese, but also with Ryukyuan, Ainu and English. Within each section the focus is on sociolinguistic matters, including language diversity, change, regulation, attitudes and controversy. A secondary aim of the chapter is to provide readers with a guide to research resources accessible in English, both on the printed page and on the internet.