In a time of intensifying great-power rivalry, the Group of 20, or G-20, has become an indispensable forum for urgent global problems. As the West enters an increasingly entrenched conflict with Russia and tensions rise between the United States and China, the G-20—which brings together 19 of the world’s largest economies along with the European Union—provides a crucial way to make progress on shared international concerns ranging from food security and financial stability to climate change.