Object-Oriented Programming (OOP) in Java is a programming paradigm that organizes software design around objects, which represent real-world entities. Java, being a pure object-oriented language, utilizes classes to define these objects, encapsulating their attributes and behaviors. This approach allows developers to break down complex problems into smaller, manageable components, enhancing code organization and reusability. Key OOP concepts in Java include encapsulation, inheritance, polymorphism, and abstraction, which collectively contribute to building scalable and maintainable applications. Understanding OOP principles is essential for effective Java programming and developing robust software solutions.