Samsung has already also confirmed that it will use its own processor in "the Next Galaxy", although it has not officially confirmed the name.
The handset will update the market-leading Galaxy SII, and will be introduced at an event at Earl's Court, London, starting at 7pm this evening, it is believed.
Unusually for a non-Apple phone launch, the 'Samsung Unpacked 2012' event is also being streamed live to members of the public online and to a special Samsung-branded branch of Phones4u on Oxford Street.
New suggestions have also emerged that the S3 will be accompanied by other devices to be launched this evening, including an official 'Olympics phone'.
Samsung has emerged as the only Android handset manufacturer capable of seriously challenging Apple. Across a broad range of devices, it already outsells the iPhone maker, although Apple remains more profitable.
Samsung overtook Apple in smartphone sales in the first quarter “in what is increasingly becoming a two-horse race”, according to Juniper Research. The two firms accounted for 60 per cent of the global smartphone market, which was 139m devices in total.
Jason Jenkins, editor of technology site CNET UK, said that "If the product is as well-received as its predecessor, the Samsung Galaxy S2, Apple has a real fight on its hands as it tries to regain the top slot."
Samsung sold 47 million devices, compared to Apple’s 35 million, but its current flagship, the Galaxy Nexus, has struggled to match the 20 million sales of the Galaxy SII.
The new device will use a Samsung processor that offers four cores and can power high-definition content.
Commentators suggest that Samsung will focus on NFC, the wireless technology that it has already confirmed it is collaborating with Visa to develop a payments platform, and that the screen will be bigger than the current device, which features a 4.3-inch display.
Rival manufacturers such as HTC have bundled online storage with their phones, while also offering improved camera technology. Other companies such as Sony have emphasised that their devices allow easy access to exclusive music and film content.
