在计算机科学中，局部变量是拥有局部作用域的变量。这样的变量只能由声明它的函数或块中访问。在仅有两层可见性的进程设计语言中，局部变量对应全局变量；另一方面，许多类ALGOL语言允许任意多层的嵌套函数，各自拥有私有变量、函数、常量和类型。

大多数进程设计语言中，局部变量是直接存储在调用堆栈上的自动变量。即递归函数调用自己时，局部变量的每一份实例都在不同的地址空间中。于是在当前作用域对变量的声明、写入、读取都不会在其被声明的函数外产生副作用。

In computer science, a local variable is a variable that is given local scope. Local variable references in the function or block in which it is declared override the same variable name in the larger scope. In programming languages with only two levels of visibility, local variables are contrasted with global variables. On the other hand, many ALGOL-derived languages allow any number of nested levels of visibility, with private variables, functions, constants and types hidden within them, either by nested blocks or nested functions. Local variables are fundamental to procedural programming, and more generally modular programming: variables of local scope are used to avoid issues with side-effects that can occur with global variables.