This lead article surveys the history and evolving policy legacies of the “one China” framework 50 years after US President Richard Nixon's historic 1972 visit to China. It begins by introducing key concepts and highlighting the crucial difference between Beijing's self-defined “one-China principle” and the US's, Japan's and key other countries’ variable “one China” policies as it relates to Taiwan. It argues that three seminal 1970s developments consolidated the “one China” framework as an informal institution of international politics. The ambiguity baked in by Cold War-era geopolitical necessity provided flexibility sufficient to enable diplomatic breakthroughs between erstwhile adversaries, but also planted seeds for deepening contestation and frictions today. Recent developments – especially Taiwan's democratization and Beijing's increasingly bold and proactive assertion of its claim to sovereignty over Taiwan – have transformed incentive structures in Taipei and for its major international partners. The net effect is that the myth of “consensus” and the ambiguities enabling the framework's half-century of success face unprecedented challenges today.