The device does not have a name yet but the flexible mobile screen technology is called the Infinity Flex Display.
The company hopes to mass produce the phone – which unfolds from a compact smartphone to a 18.5cm (7.3in) tablet- “in the coming months”.
There is also a secondary screen that can be used when the phone is in a compact mode.
DJ Koh, who heads Samsung’s IT and mobile communications division, said: “The foldable display lays the foundation for a new kind of mobile experience.”
The company will be working with Android developers to discover the best uses for the foldable phone, which is set to enter producton within months.
“We are excited to work with developers on this new platform to create new value for our customers. We cannot wait to see where the technology and collaboration takes us,” added Koh.
Samsung obscured the final look of its device. It placed it in a case to hold off revealing the design until a later event. It also did not disclose how it will brand the phone.
However, it did reveal that the forthcoming handset would be able to run three apps at once.
Justin Denison, the executive who unveiled the handset, noted that when folded up the device fitted “neatly inside” a jacket pocket thanks to the displays involved being thinner than those on earlier phones.
Samsung is facing tough competition to deliver its foldable smartphone, with Royale Corporation, a California-based tech company, unveiling its challenger in Beijing last week.