Windows Installer是在Windows 2000时提出，作为微软操作系统中的安装程序开发标准的操作系统服务。它可以支持安装程序所需要的许多功能，并且可以支持交易式安装（Committable Installation），当安装程序发现错误或问题时，可以将安装进程中所做的任何修改（包含复制文件、修改组态等）全部回溯为未变更的状态。

目前Windows Installer最新版本为5.0版。

Windows Installer (previously known as Microsoft Installer) is a software component and application programming interface (API) of Microsoft Windows used for the installation, maintenance, and removal of software. The installation information, and optionally the files themselves, are packaged in installation packages, loosely relational databases structured as COM Structured Storages and commonly known as "MSI files", from their default filename extensions. Windows Installer contains significant changes from its predecessor, Setup API. New features include a GUI framework and automatic generation of the uninstallation sequence. Windows Installer is positioned as an alternative to stand-alone executable installer frameworks such as older versions of InstallShield and NSIS.