运行时期(Run time)在计算机科学中代表了一个电脑程序运作、运行的时期，从开始运行到终止运行。与运行时期相对的其他时期包括：设计时期(design time)、编译时期(compile time)、链结时期(link time)、与加载时期(load time)。

而运行环境是一种为正在运行的进程或程序提供软件服务的虚拟机械环境。它有可能是由操作系统自行提供，或由运行此程序的母程序提供。

通常由操作系统负责处理程序的加载：利用加载器(loader)读入代码，接着进行基本的内存配置，并视需要联结此程序指定的所有动态数据库。有些编程语言会由此语言提供的运行环境处理上述工作。

In computer science, run time, runtime or execution time is the time during which a program is running (executing), in contrast to other program lifecycle phases such as compile time, link time and load time.

A run-time error is detected after or during the execution (running state) of a program, whereas a compile-time error is detected by the compiler before the program is ever executed. Type checking, register allocation, code generation, and code optimization are typically done at compile time, but may be done at run time depending on the particular language and compiler.