“Nudge units” within governments, most notably in the United Kingdom and the United States, seek to encourage people to behave a certain way by using insights gained from behavioral science. The aim is to influence people’s choices through policies that offer the right incentive or hurdle so that people choose the more economically beneficial options. Getting people to save for retirement, eat more healthful foods, and pay their taxes on time are some examples of institutionally desirable activities. The 10-fold rise in “nudge” projects undertaken since 2010—more than 20 countries have deployed or expressed interest in them—have revealed many lessons for policymakers. Chief among these lessons: the necessity of obtaining buy-in from key political leaders and other stakeholders, and the benefits of testing multiple intervention strategies at once. Although detailed cost–benefit analyses are not yet available, we estimate that behaviorally inspired interventions can help government agencies save hundreds of millions of dollars per year.