Mobile networks O2 and Vodafone are launching their 4G data services for the first time.
O2's service will initially be switched on in London, Leeds and Bradford, reaching up to five million people from the launch, while Vodafone will roll its service out in parts of the capital.
Both networks plan to have network coverage in 13 cities by the end of the year - London, Birmingham, Bradford, Coventry, Edinburgh, Glasgow, Leeds, Leicester, Liverpool, Manchester, Newcastle, Nottingham and Sheffield - and both plan eventually to provide 4G coverage to 98% of the population.
The launches follow on the heels of EE, which has offered "super-fast" 4G mobile data in the UK since October last year.
4G - fourth generation networks - can provide data to smartphone users on average six times faster than 3G connections, Vodafone said.
Vodafone spent £802 million when it bid for part of the mobile phone spectrum to provide 4G, while O2 spent £550 million to buy a proportion of the lowest frequency spectrum.