Microsoft Cluster Server (MSCS) is computer program that allows servers to work together as a computer cluster, to provide failover and increased availability of applications.

Microsoft has three technologies for clustering: Microsoft Cluster Service (MSCS), Component Load Balancing (CLB) , and Network Load Balancing Services (NLB). In windows Server 2008  the MSCS service has been renamed to Windows Server Failover Clustering and the Component Load Balancing (CLB) feature has been deprecated.