USB大容量存储设备（英语：USB mass storage device class）是一个协议，允许一个USB接口的设备与主计算设备相连接，以便在两者之间传输文档。对于主计算设备来说，USB设备看起来就像一个移动硬盘，允许拖放型文档传送。它实际上是由USB实施者论坛所通过许多通讯协议的汇总，这一标准提供了许多设备的界面。包括移动硬盘、闪存盘、移动光学驱动器、读卡器、数码相机、数码音乐播放器、PDA以及手机等等。

The USB mass storage device class (also known as USB MSC or UMS) is a set of computing communications protocols defined by the USB Implementers Forum that makes a USB device accessible to a host computing device and enables file transfers between the host and the USB device. To a host, the USB device acts as an external hard drive; the protocol set interfaces with a number of storage devices.