Almost a third of UN member states still criminalize private same-sex sexual conduct between consenting adults and many punish such conduct with severe penalties. Such criminalization—irrespective of enforcement—stigmatizes and discriminates against LGBTIQ persons, sustaining an intolerant social environment conducive to various forms of violence against them and denial of their human rights. The first part of this chapter focuses on the trajectory of criminalization: its religious roots in the Bible, the secularization of the crime of sodomy in England in 1533 and its worldwide expansion through (British) colonialism, and its contemporary defences in parts of the Global South, based on a combination of anti-Western/anti-colonial sentiment, cultural relativist arguments, and conservative narratives of traditional religious and family values. The second part tells the story of decriminalization: its liberal origins in the Enlightenment and in Mill’s harm principle, the evolving international human rights legal framework, and the case law of the European Court of Human Rights and other international and regional courts and treaty bodies on the right to private life and non-discrimination, which has led to an ongoing wave of decriminalization through legislative reforms and especially domestic judicial decisions, particularly in commonwealth jurisdictions.