Social scientists of all kinds, from anthropologists to economists, are aware of the deep changes that globalization has brought to our world. Global legal history can be either a field or an approach in which legal history, comparative law, and a global perspective converge. Global legal history assumes a denationalization of its perspective. Global legal history, therefore, takes law as a general normative practice, varying across time and space, drawing comparisons among experiences in different times and places, and searching for the existence of ideas, rules, and institutions common to different societies. The law was never constructed in a closed or autopoietic way, as some have believed, because even in those centuries cross-pollination between the national legal systems was too extensive, as the examples illustrate. The chapter also presents an overview of the key concepts discussed in this book.