`std::overflow_error` is an exception class in the C++ Standard Library that indicates an arithmetic overflow has occurred. This situation arises when a calculation produces a result that exceeds the maximum limit of the data type being used, such as when adding two large integers. It helps programmers identify and handle errors related to arithmetic operations more effectively. When an overflow occurs, the program can throw a `std::overflow_error` exception, allowing developers to catch it and take appropriate action, such as logging the error or adjusting the input values. This mechanism enhances the robustness of applications by preventing unexpected behavior due to overflow conditions.