This chapter explores the historical context of the international ideas and ideologies driving the deinstitutionalisation reform. It sets out with a brief overview of the institutional era and the developments leading to the fall of institutions, including overcrowding, warehousing, and inhumane treatment. The bulk of the chapter, however, addresses the radical change from institutional incarceration to community-based services. This change is explored through the lives and work of three leaders of the reform: Niels Erik Bank-Mikkelsen, Bengt Nirje and Wolf Wolfensberger. All three are considered “classic” pioneers in conceptualising the principle of normalisation, the ideology guiding the deinstitutionalisation reform. The chapter examines their historical context and explores the origin of their ideas and what inspired them in creating humane conditions and equal rights for people with intellectual disabilities. The chapter describes how normalisation was embraced internationally as a guiding principle to close institutions and develop community-based services. It concludes by discussing the complex difficulties and barriers in implementing normalisation which led an increasing number of people to lose faith that normalisation could deliver what it promised.