The 60 years that followed a study of mathematics in 12 countries conducted by the International Association for the Evaluation of Educational Achievement (IEA) in 1964 have seen a proliferation of large‐scale assessments (LSAs) in education. In a recent systematic review of the impact of LSAs on education policy (Best et al., 2013), it was estimated that LSAs in education are now being undertaken in about 70% of the countries in the world. The Programme for International Student Assessment (PISA) conducted by the Organisation for Economic Co‐operation and Development (OECD) was implemented in 75 countries in 2015 with around 510 000 participating students and their schools. Similarly, the Trends in International Mathematics and Science Study (TIMSS), conducted by the IEA, collected information from schools and students in 59 countries in 2015. This introductory chapter first provides some context in terms of the development of international, regional and national assessments and the policy context in which they occur. Then, the purposes for countries to undertake such assessments, particularly with a view to evidence‐based policymaking in education, are discussed. This is followed by a description of the content of the book. The chapter finishes with considerations as to where LSAs might be headed and what is likely to shape their development.