Technology company Apple has released its first folding smartphone that has the largest screen of any iPhone.

Called iPhone Duo, the phone is the first folding-screen device in Apple's product lineup. It features a central hinge mechanism as well as an external screen visible when the device is folded.

"[iPhone Duo] redefines the experience of using a foldable phone," said Apple CEO John Ternus during a Wednesday virtual presentation.

It marks the entry of the company into the foldable screen market. It is the first major change in the phone's form since Apple released its first touchscreen phones in 2007.

Apple vice president of industrial design Molly Anderson said that the phone, when folded, is around the same size as a passport. When folded, it measures 5.4 inches long with about 90 per cent of the aspect ratio of the iPhone 18 Pro, also announced today.

Anderson added that the phone is the "largest iPhone display ever designed" when unfolded at 7.6 inches. It has a titanium enclosure and "ceramic shields" on the front and back of the shell.

The screen also allows the front-facing camera to be covered by the display.

It features a central hinge with a "variable torque profile" and over 100 components so that the device can sit partially open. It can be used in this semi-open state, held like a book or placed on a surface like a laptop computer.

The screen component has multi-layered lamination with scratch-resistant glass on the top.

It has speakers on two sides, and the external and internal screens have the same aspect ratio.

Two external cameras were integrated with the company's upgraded aperture features.

The company also released custom cases for the product, one with a "kickstand".

Ternus said that the foldable phone was the best way to make the iPhone an "intelligent personal hub".

Apple announced updates to its other products, including the iPhone 18, set to release next year, as well as a new edition of the Apple Watch.

It also updated its vapour chamber cooling systems, integrating recycled steel and a copper plate.

The release comes nearly 20 years after Apple first released the iPhone in 2007 under then-design officer Jony Ive.

The folding OLED-screen phone has been tried by a number of other companies. Samsung's Galaxy Fold was released in 2019. Last year, Chinese company Honor released a folding phone that it claims is the "world's thinnest".

The images are courtesy of Apple.