A personal digital assistant (PDA), also known as a handheld PC, is a variety mobile device which functions as a personal information manager. PDAs have been mostly displaced by the widespread adoption of highly capable smartphones, in particular those based on iOS and Android, seeing a rapid decline in use after 2007.

A PDA has an electronic visual display. Most models also have audio capabilities, allowing usage as a portable media player, and also enabling many of them to be used as telephones. By the early 2000's, nearly all PDA models had the ability to access the Internet, intranets or extranets via Wi-Fi or Wireless WANs, and generally include a web browser. Sometimes, instead of buttons, PDAs employ touchscreen technology.

The first PDA, the Organiser, was released in 1984 by Psion, followed by Psion's Series 3, in 1991. The latter began to resemble the more familiar PDA style, including a full keyboard. The term PDA was first used on January 7, 1992 by Apple Inc. CEO John Sculley at the Consumer Electronics Show in Las Vegas, Nevada, referring to the Apple Newton. In 1994, IBM introduced the first PDA with analog cellular phone functionality, the IBM Simon, which can also be considered the first smartphone. Then in 1996, Nokia introduced a PDA with digital cellphone functionality, the 9000 Communicator. Another early entrant in this market was Palm, with a line of PDA products which began in March 1996. Palm would eventually be the dominant vendor of PDAs until the rising popularity of Pocket PC devices in the early 2000s. By the mid-2000s most PDAs had morphed into smartphones as classic PDAs without cellular radios were increasingly becoming uncommon.