The main function of an API gateway is to manage, route, and secure application program interfaces (APIs) for applications. It acts as a single entry point for client requests, handling tasks like request authentication, rate limiting, and load balancing, ensuring consistent access to back-end services. By centralizing these functions, API gateways enhance security and simplify management, allowing developers to focus on creating functionality rather than on infrastructure concerns. They’re vital in microservices architectures, enabling seamless communication between components.