The main aim of this chapter is to provide an introduction to an important aspect of the Corpora/ELT relationship, i.e. the link between corpora and ESP (English for Specific Purposes). Throughout this book, we have discussed the case for a corpus-informed approach to ELT and it can be argued that, in relation to ESP, the case for a corpus-informed approach to teaching and materials design is even stronger, as it is not unusual for English language teachers to find themselves teaching English for specialisms of which they have no particular knowledge. I have myself, for example, taught English to an engineer and to an opera singer, even though I find changing a light bulb and singing a note challenging (especially at the same time). This link between corpora and ESP is likely to remain important for some time to come, given the current patterns of academic and professional mobility which create a need for ESP expertise and materials, so it is an area that clearly deserves our attention from both a research and practitioner perspective.