Since the Global Financial Crisis, fiscal policy in advanced economies has become more “active” – that is, increasingly unresponsive to rising debt levels. This paper explores tensions between active fiscal and monetary policies by introducing the concept of “fiscal r-star,” which is the real interest rate required to stabilize debt levels when the primary balance is set exogenously, output is growing at potential, and inflation is at target. It is proposed that the difference between monetary r-star and fiscal r-star—referred to as the “fiscal monetary gap”—is a proxy for fiscal-monetary policy tensions. An analysis of over 140 years of data from 16 advanced economies shows that larger fiscal-monetary gaps are associated with rising debt levels, higher inflation, financial repression, lower real returns on bonds and cash, with elevated risks of future debt, inflation, currency, housing, and systemic crises. Current estimates indicate that fiscal-monetary tensions are at historic highs. Given the tepid growth outlook, growth-enhancing reforms and fiscal consolidation, among other policy adjustments, may be needed to attenuate fiscal-monetary tensions over time.