Free access for the first month will be provided in association with Nokia, allowing anyone with a Wi-Fi enabled device to get online without paying for access.
"Metropolitan Wi-Fi networks are changing the face of towns and cities around the world for public access and public sector applications," said Niall Murphy, co-founder and chief strategy officer at The Cloud.
"The City of London network is a global benchmark for cities and metro Wi-Fi, and an exciting addition to The Cloud's network across the UK and our other city networks in Europe."
The system, which its creator claims is Europe's densest, most comprehensive city-wide Wi-Fi network, was the product of 12 months' development and testing.
Coverage is provided using mobile broadband 'mesh' technology supplied by BelAir Networks, and currently comprises 127 nodes which will be expanded to offer 95 per cent coverage across areas owned by the City of London Corporation.
The City-wide network has been designed and built onto existing street furniture including lamp posts and street signs.
Michael Snyder, chairman of the City of London's Policy Committee, said: " The City of London is the world's leading financial and business centre and has always benefited from a world class communications infrastructure.
"It is therefore important that we provide the latest technology that will benefit those working in or visiting the City."
The Cloud is currently in talks with other London boroughs to roll out the system, but no dates or regions have been specified as yet.
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