The trial of 4G, also known as Long Term Evolution (LTE), will run for nine months in London and involve O2 giving hundreds of consumers, businesses and venue owners access to its new 4G network.
O2 said that more than 25 4G sites will go live across the capital this month, covering a combined area of 40 square kilometres stretching from Hyde Park to The O2 Arena in Greenwich, and covering Canary Wharf, Soho, Westminster, South Bank and Kings Cross.
The 4G network will enable O2 to provide mobile broadband of similar speeds to fast home internet connections over fibre networks, allowing users to watch high definition films and play online gaming on their smartphones and tablets.
It is hoped that 4G technology will provide a solution to the ever growing consumer demand for mobile data, as well as deliver a significant boost to the UK's broadband network.
BT has already partnered with mobile carrier Everything Everywhere - a joint venture between Orange and T-Mobile - to launch a live customer trial of next-generation 4G mobile broadband in Cornwall.
Using the new technology, O2 said participants in its London-based trial will be able to download a 500MB file in around one minute, compared to over five minutes on current 3G services.
Ronan Dunne, the chief executive of O2 parent company Telefónica UK, said: "Today's launch of the UK's first 4G London trial network demonstrates our commitment to delivering 4G to our customers at the earliest opportunity. The work we are doing now will lay the foundations for our commercial 4G network when it launches in the UK."
Retail chain John Lewis will also be involved in the trial as one of O2's largest corporate customers, while the Institution of Engineering and Technology will try out the new technology.
The 4G trial will use the 2.6GHz spectrum band under a special test and development licence granted to O2 by media regulator Ofcom. The 2.6GHz band can support 4G LTE speeds of up to 150Mbps.
O2 said that data drawn from the pilot will be used "to influence and shape O2's plans for the commercial implementation of its forthcoming 4G network".
This comes ahead of Ofcom's proposed auction of 4G spectrum which is expected to take place in the first half of 2012, although it has been delayed due to the threat of legal action from the mobile carriers.
"O2 has been at the heart of the mobile data explosion over the last three years and our priority has always been to build ahead of the curve," continued Dunne.
"Our work in London will give us a better understanding of the capabilities of 4G technology and will allow us to explore the superfast benefits it will bring to people and industry across the UK. This 4G trial is the next step on our journey to a smarter network - a network that offers a seamless, connected experience across multiple devices, locations and services.
"The forthcoming spectrum auction is a watershed moment for the UK mobile industry, which will see the release of the airwaves capable of powering a whole range of exciting next-generation mobile services. We are actively engaged in the auction and are supportive of a fair process that meets the government's and Ofcom's planned timeline."
> 4G to boost mobile capacity by 200%, says Ofcom