Sexual Orientation and Gender Identity have “come out of the closet” in the academic debate since more than fifty years. In the humanities Gay and Lesbian Studies, Queer Studies, or Diversity Studies have produced a number of important publications on Lesbian, Gay, Bisexual, Transgender, and Intersex (LGBTI) persons. In the legal literature, however, LGBTI issues have been addressed in more depth since the 1990s only. Most of these studies are legal guides or journal articles on specific domestic legal systems (in particular the US). In addition, very few regional and international bodies have been addressed in the literature (normally the UN and European institutions like the EU and the Council of Europe). While some inter-governmental bodies and NGOs have undertaken important work on human rights aspects of the topic and the related case law, there is no comprehensive and accurate yet concise (teaching) manual on the common problems faced by LGBTI persons worldwide and the domestic and international legal responses to it. Maybe the questions of marriage or civil partnership and adoption have benefitted from increased comparison in recent years, but other aspects are not covered well or in an easily accessible and accurate way. The purpose of this book is to bring together some of the major experts from both academia and governmental and non-governmental institutions involved in the research in the field in order to allow the reader to get an introduction to the main problems and the legal responses from an international (including regional cooperation initiatives) and comparative perspective. The goal is not to collect the data on each and every jurisdiction in the world but to identify and analyze common legal patterns and trends regarding sexual orientation and gender Identity and to present the possible solutions for the remaining challenges. The expected audience are those teaching LGBTI courses worldwide thereby allowing them to develop the comparative and international aspects in addition to purely national approaches . In addition, there are a great number of students, politicians, journalists, opinion leaders and activists in need of a proper legal introduction to the field. This is an increasingly relevant area of human rights research that is still in lack of a proper handbook.