NTBackup (or Windows Backup) is the built-in backup application introduced in Windows NT 3.51 and included in Windows NT 4.0, Windows 2000, Windows XP, and Windows Server 2003. NTBackup comprises a command-line utility and a set of wizard interfaces that provide multiple options to create, customize, and manage backups, and it is integrated with Shadow Copy and Task Scheduler. NTBackup creates backups in a proprietary BKF file format to external sources including floppy disks, hard drives, tape drives, and ZIP drives.

NTBackup is replaced by Backup and Restore and WBAdmin starting with Windows Vista, which provide similar functionality and instead use the Virtual Hard Disk file format to backup content; however, in Windows Vista, it is possible to restore NTBackup by copying necessary files from Windows XP. Windows Server Backup replaces NTBackup beginning with Windows Server 2008; neither Backup and Restore nor Windows Server Backup support the use of tape drives.

For reading/restoring older backups, Microsoft has made available the NTBackup Restore utility for Windows Vista/Windows Server 2008 and for Windows 7/Windows Server 2008 R2 which can only read BKF files.

When used with tape drives, NTBackup uses the Microsoft Tape Format (MTF), which is also used by BackupAssist and Backup Exec and Veeam Backup & Replication and is compatible with BKF.