Windows Server 2003是微软的服务器操作系统，对应Windows XP。

该产品最初叫作“Windows .NET Server”，后改成“Windows .NET Server 2003”，最终被改成“Windows Server 2003”，于2003年3月28日发布，并在同年四月底上市。

相对于Windows 2000，此版本做了很多改进，特别是：

Windows Server 2003 (sometimes informally referred to as Win2**, or just 2**) is a server operating system produced by Microsoft and released on April 24, 2003. It was a successor of Windows 2000 Server and incorporated some of Windows XP features. An updated version, Windows Server 2003 R2, was released to manufacturing on December 6, 2005. Its successor, Windows Server 2008, was released on February 4, 2008. Windows Server 2003's kernel was later adopted in the development of Windows Vista.