Boris Johnson was joined by the ICC London Excel and London & Partners to make the announcement this morning (3 October).
The Mayor said he wanted to demonstrate to the global events industry that London is focused on continuing its success in business tourism.
"There are fantastic opportunities in London for smaller conferences and business events," said Johnson.
He added the aim is to carry on transforming the perception of the city as a leading congress destination.
The ESC is expected to attract 35,000 delegates from 29 August to 2 September 2015.
Johnson said: "This means not just a filip for London as a centre of medical study but also a massive boost to our reputation as a business traveller's venue.
"Conferences of this kind are estimated to bring £80m of economic benefit to the host and I am very pleased to support it."
Excel London chief executive Kevin Murphy added the event would help London rise further up the ICCA rankings, from its current 7th position.
Other cities shortlisted were Munich, Stockholm, Barcelona and Vienna.
"This is a reputation changing event for London," added Murphy. "It is fantastic news for UK plc, for London and for Excel."
He added he was "constantly sending the message to central government" of the value of business events.