The English language is widely taught and learned around the world, and a very large field of research investigates the teaching and learning of English. This broad area of teaching and research activity is known as Teaching English to Speakers of Other Languages (TESOL). This chapter reviews the interests and issues which fall under the heading of TESOL and describes the development of the field. It then goes on to identify issues of current relevance to TESOL, such as the status of English as a global lingua franca, and role and position of TESOL teachers. The chapter closes by identifying questions, such as whether English will maintain its dominant position in the global linguistic landscape, which will affect TESOL in the future.