With the development of transitional justice, international transitional justice law has been growing and has become a branch of international law. On the one hand, practices and mechanisms, mainly to respond to international law violations in times of transition or after an armed conflict, have been contributing to the development of this branch of international law. On the other hand, international law has been progressively defining international obligations of states in the field of transitional justice, even if there is still room for improvement. This book aims to introduce and analyse transitional justice within the field of international law, examining its emergence, international diffusion, processes, and mechanisms, as well as the international legal norms mobilised in this area.