The Antarctic and the Arctic are at present among the fastest changing areas on the Earth, particularly as a consequence of anthropogenic climate change. This Chapter provides a broad introduction to environmental change regarding the Polar regions, by looking at the parameters of the ongoing change—not least its speed and scale—against the background of the Earth’s geological history. First, the settings—the Antarctic and the Arctic—are introduced through a brief review from the onset of glaciation at the North Pole in the Quaternary Period, to the circumstances of the present interglacial interval, the Holocene Epoch, and the onset of the Industrial Revolution and its effects in the late Holocene, to the onset of changing conditions in the Polar regions. The next section places the Polar regions in a new context, the Anthropocene: first, the concept of the Anthropocene, as introduced in the natural sciences and thereafter geology, is explained; secondly, the drivers of the ongoing change as related to the Poles are discussed; thirdly, the manifestations so far in the Arctic and the Antarctic, especially regarding the pattern and rate of ice mass loss, are presented; and fourthly, changes expected in the rest of the twenty-first century are outlined. Finally, this Chapter concludes by pointing to the interconnections between the Poles and the globe, both regarding the mechanisms at work in the Earth System and the legal and political frameworks currently available to respond to the challenges involved. We conclude that interconnecting the ‘global’ with the ‘Polar’ on the background of changing Earth System conditions will become a vital task for both policy-makers and international law scholars in the decades to come, when the development of international law will necessarily—and progressively—become led by complex drivers characterizing the Anthropocene, including changes in coastline forced by changing sea level.