Three will launch its 5G home broadband service first, with customers in London to get the ability to switch their internet connection to a cable-free, superfast alternative in just a couple of months.
It will then follow-up by expanding its 5G mobile network to 25 cities and towns by the end of the year.
The locations to be switched-on in the first batch are Birmingham, Bolton, Bradford, Brighton, Bristol, Cardiff, Coventry, Derby, Edinburgh, Glasgow, Hull, Leeds, Leicester, Liverpool, London, Manchester, Middlesbrough, Milton Keynes, Nottingham, Reading, Rotherham, Sheffield, Slough, Sunderland and Wolverhampton.
Three claims that it has more 5G spectrum that the other big UK operators and that its network will be capable of hitting peak speeds that are "at least 2x faster" than its rivals.
It holds spectrum in the 140MHz block, including access to a 100MHz contiguous black that can potential provide faster 5G speeds. Other operators hold 40MHz and 50MHz blocks - including the already-launched EE network, plus Vodafone's that will launch in July.
Future 5G plans include the goal to have 80 per cent of its network traffic covered by 5G by 2022. Those sticking with 4G should also get a boost too, as the company is hoping to deliver "up to 400 per cent improvements in 4G speed and capacity" by deploying more 4G spectrum, converting 3G spectrum and upgrading its antennas as part of a £2 billion investment in its infrastructure.
"We have worked hard over a long period of time to be able to offer the best end-to-end 5G experience. 5G is a game changer for Three," said company CEO Dave Dyson.