APIs (Application Programming Interfaces) play a crucial role in facilitating cross-platform integration by enabling different software systems to communicate with each other seamlessly. They define a set of rules and protocols for how applications interact, allowing for data exchange and functionality sharing without needing to understand the internal workings of the system. APIs enhance interoperability, making it easier to build composite applications that leverage services from multiple platforms. As a result, organizations can create more versatile solutions that improve user experiences and operational efficiency.