This article studies the interaction between takeover defenses and competition. We find that firms in more competitive industries have more takeover defenses. This suggests that product market competition can be a substitute for the market for corporate control, with more information available in competitive markets making monitoring less costly. A novel instrument for the incentives of stakeholders in the product market to monitor is provided by the nature of the relationship between the firm and its customers. For firms in industries with long-term relationships with customers and suppliers, these stakeholders have greater incentives to monitor. We document that stronger competition is linked to more defenses only in these “relationship” industries. Finally, we discuss the implications for the design of other governance mechanisms.