FastAPI is a high-performance web framework for building APIs with Python. It is designed to be fast, easy to use, and highly scalable, allowing developers to quickly build and deploy production-ready APIs. FastAPI leverages the latest features of Python 3, including type annotations and async/await syntax, to provide fast, efficient, and type-safe code. Its built-in features also enable automatic API documentation generation and support for data validation, making it a popular choice for building modern and robust web applications.