The system partition and the boot partition (also known as the system volume and the boot volume) are computing terms for disk partitions of a hard disk drive or solid-state drive that must exist and be properly configured for a computer to operate. There are two different definitions for these terms: the common definition and the Microsoft definition.

Common definition

In context of every operating system, except those developed by Microsoft, the system partition and the boot partition are defined as follows: In Linux, a single partition can be both a boot and a system partition if both and the root directory are in the same partition.

Microsoft definition

Since Windows NT 3.1 (the first version of Windows NT), Microsoft has defined the terms as follows: Before Windows 7, the system and boot partitions were, by default, the same and were given the "C:" drive letter. Since Windows 7, however, Windows Setup creates, by default, a separate system partition that is not given an identifier and therefore is hidden. The boot partition is still given "C:" as its identifier. This configuration is suitable for running BitLocker, which requires a separate unencrypted system partition for booting. As of Windows 11, this nomenclature is still used by the "Disk Management" utility.