We show that the supply of U.S. life annuities is constrained by interest rate risk. We identify this eect using annuity prices oered by life insurers from 1989 to 2019 and exogenous variations in contract-level regulatory capital requirements. The cost of interest rate risk management|conditional on the effect of adverse selection|accounts for about half of annuity markups, or 8 percentage points. The contribution of interest rate risk to annuity markups sharply increased after the Global Financial Crisis, suggesting new retirees' opportunities to transfer their longevity risk are unlikely to improve in a persistently low interest rate environment.