Aging of a eukaryotic organism is affected by its nutrition state and by its ability to prevent or repair oxidative damage. Consequently, signal transduction systems that control metabolism and oxidative stress responses influence life span. When nutrients are abundant, the insulin/IGF signaling (IIS) pathway promotes growth and energy storage but shortens life span. The transcription factor Foxo, which is inhibited by IIS, extends life span in conditions of low IIS activity. Life span can also be increased by activating the stress-responsive Jun-N-terminal kinase (JNK) pathway. Here we show that JNK requires Foxo to extend life span in Drosophila. JNK antagonizes IIS, causing nuclear localization of Foxo and inducing its targets, including growth control and stress defense genes. JNK and Foxo also restrict IIS activity systemically by repressing IIS ligand expression in neuroendocrine cells. The convergence of JNK signaling and IIS on Foxo provides a model to explain the effects of stress and nutrition on longevity.