To better understand potential relationships between income and terrorism, we study data for 1,527 subnational regions in 75 countries between 1970 and 2014. Results consistently imply an inverted U-shape that remains robust to accounting for a comprehensive set of region-level covariates, region- and time-fixed effects, as well as estimating an array of alternative specifications. The threat of terrorism systematically rises as low-income polities become richer, peaking at an income level of about US$12,800 per capita (in constant 2005 PPP US$), but then falls consistently above that level. This pattern emerges for domestic and transnational terrorism alike. Peaks in the income-terrorism relationship differ by perpetrator ideology. Thus, alleviating poverty per se may first exacerbate terrorism, contrary to much of the proposed recipes advocated since 9/11.