A foldable smartphone is a smartphone with a folding form factor. It is reminiscent of the clamshell design of many earlier feature phones. Some variants of the concept use multiple touchscreen panels on a hinge, while other designs utilise a flexible display. Concepts of such devices date back as early as Nokia's "Morph" concept in 2008, and a concept presented by Samsung Electronics in 2013, while the first commercially available folding smartphones with OLED displays began to emerge in November 2018.

A clamshell design is a kind of form factor for electronic devices in the shape of a clamshell. Mobile phones, handheld game consoles, and especially laptops, are often designed like clamshells. Clamshell devices are usually made of two sections connected by a hinge, each section containing either a flat panel display or an alphanumeric keyboard/keypad, which can fold into contact together like a bivalve shell.