We use club theory for the first time to provide a model of Securities Exchange (SX) formation. We think of a SX as a local public good that allows its traders to diversify risk by trading their securities with other SX members. In our two-stage equilibrium setting, traders evaluate SXs depending on their risk-sharing possibilities, and, given these evaluations, choose the SX they want to join. Security prices can differ among SXs and traders may value SX memberships differently. We establish continuity properties in both stages and show that equilibrium exists for a generic set of economies.