快闪随身碟（又称USB随身碟、快闪随身碟、USB内存、U盘、U盘、电子盘、随身碟、记忆棒、手指、随存、大姆哥），发明者尚有争议，中国的科技公司朗科科技声称发明了U盘。U盘的称呼最早来源于朗科科技生产的一种新型存储设备，名曰“U盘”。它是一种使用USB接口连接计算机，并通常通过闪存来进行数据存储的小型便携存储设备。一般U盘体积极小、重量轻、可重复写入，面世后迅速普及并取代传统的软碟及软驱。有时读卡器也会被归类为随身碟。这类设备的记忆芯片并不是内置的，而是可以抽换的记忆卡。

相较于其他可携式保存设备（尤其是软碟），U盘有许多优点：较不占空间、能保存较多数据、读写速度较快、不会因刮伤或发霉而无法使用。这类的USB存储设备使用USB大量保存设备标准，在近代的操作系统如Windows、OS X、Linux与Unix中皆有内置支持。

A USB flash drive, also commonly known as a USB drive, USB stick and a variety of other names, is a data storage device that includes flash memory with an integrated USB interface. USB flash drives are typically removable and rewritable, and physically much smaller than an optical disc. Most weigh less than 30 grams (1.1 oz). As of January 2013, drives of up to 512 gigabytes (GB) were available. A one-terabyte (TB) drive was unveiled at the 2013 Consumer Electronics Show and became available later that year. Storage capacities as large as 2 TB are planned, with steady improvements in size and price per capacity expected. Some allow up to 100,000 write/erase cycles, depending on the exact type of memory chip used, and have a 10-year shelf storage time.