The API lifecycle refers to the stages an API goes through from creation to retirement. It typically includes planning, design, implementation, testing, deployment, management, and retirement. During planning, the API's purpose, functionality, and target audience are defined. In the design phase, the API's structure, endpoints, and data formats are established. Implementation involves writing the code to create the API. Testing ensures the API works as intended. Deployment makes the API accessible to users. Management involves monitoring, securing, and updating the API. Finally, retirement is the process of phasing out the API when it is no longer needed.