How does priming identity affect charitable giving? We show that individuals are more likely to donate when a facet of their identity associated with a norm of generosity is primed in an appeal. In large charitable giving field experiments run by the American Red Cross, appeals that prime an individual’s identity as a previous donor to the charity or as a member of a local community generate more donations. The primes are more effective when they highlight a facet of the potential donor’s identity that we hypothesize to be more relevant to his sense of self: priming identity as a previous donor is more effective for more regular donors and priming identity as a local community member is more effective for people in smaller communities. Together, these results elucidate the impact of identity on behavior and demonstrate how identity primes can be implemented in practice to encourage public good provision. This paper was accepted by Uri Gneezy, behavioral economics.