迭代器（iterator）有时又称光标（cursor）是编程的软件设计模式，可在容器对象（container，例如链表或数组）上遍访的接口，设计人员无需关心容器对象的内存分配的实现细节。

各种语言实作迭代器的方式皆不尽同，有些面向对象语言像Java, C#, Ruby, Python, Delphi都已将迭代器的特性内置语言当中，完美的跟语言集成，我们称之隐式迭代器（implicit iterator），但像是C++语言本身就没有迭代器的特色，但STL仍利用模板实作了功能强大的迭代器。STL容器的数据的内存地址可能会重新分配（reallocate)，与容器绑定的迭代器仍然可以定位到重新分配后的正确的内存地址。

In computer programming, an iterator is an object that enables a programmer to traverse a container, particularly lists. Various types of iterators are often provided via a container's interface. Though the interface and semantics of a given iterator are fixed, iterators are often implemented in terms of the structures underlying a container implementation and are often tightly coupled to the container to enable the operational semantics of the iterator. Note that an iterator performs traversal and also gives access to data elements in a container, but does not perform iteration (i.e., not without some significant liberty taken with that concept or with trivial use of the terminology). An iterator is behaviorally similar to a database cursor. Iterators date to the CLU programming language in 1974.