An Input Iterator is a type of iterator in programming that allows you to read data from a collection, such as an array or a list, one element at a time. It provides a way to traverse through the elements without modifying them, ensuring that the original data remains unchanged. Input iterators are commonly used in algorithms that require reading data, such as searching or filtering. Input iterators typically support operations like incrementing to the next element and dereferencing to access the current element. They are an essential part of the C++ Standard Template Library (STL), where they help in processing collections efficiently.