A Mock Object is a simulated object that mimics the behavior of real objects in controlled ways. It is commonly used in software testing to isolate specific components, allowing developers to test functionality without relying on external systems or dependencies. This helps ensure that tests are reliable and focused on the unit being tested. Mock objects can be configured to return predefined responses, track interactions, and verify that certain methods were called. This makes them valuable in unit testing frameworks, such as JUnit or Mockito, where they help developers ensure that their code behaves as expected under various conditions.