Windows Server 2008是微软的一个服务器操作系统，继承Windows Server 2003。Windows Server 2008在进行开发及测试时的代号为Windows Server "Longhorn"。

Windows Server 2008是一套和Windows Vista（代号为Longhorn）相对应的服务器操作系统，两者拥有很多相同功能。与Windows 2000的Professional版和Server版一样，两者在开发时共用大多数的代码，连Service Pack皆可共用；Vista和Server 2008、XP和Server 2003间存在相似的关系。（XP和Server 2003的代号分别为Whistler及Whistler Server）

Windows Server 2008 (sometimes abbreviated as "Win2K8" "WinServer2K8" "Windows 2008" or "W2K8") is one of Microsoft Windows' server line of operating systems. Released to manufacturing on February 4, 2008, and officially released on February 27, 2008, it is the successor to Windows Server 2003, released nearly five years earlier. A second release, named Windows Server 2008 R2, was released to manufacturing on July 22, 2009.