Bristol has won the bid to be European Green Capital 2015, beating off competition from Brussels.
The city was considered one of the favourites for the title having finished first or second in all 12 technical categories during the initial bid stage.
Brussels, Glasgow and Ljubljana were also in the running for the title, which was announced by Janez Potocnik, European commissioner for the environment, in Nantes, the home of the current holder.
Bristol Mayor George Ferguson said: "This demonstrates Bristol's ambition to be a pioneering green city and is recognition for the many years of hard work and dedication by the city council, businesses and the people of Bristol to make our city more environmentally friendly.
"We will now be turning our attention to staging an inspiring programme of events in 2015 which will be centred around the idea of Bristol as a 'Laboratory for Change'.
"I have offered Bristol as a test-bed for environmental ideas in 2015, where we will develop pioneering practices which will not only benefit Bristol, but will hopefully become a model for cities around the world."
Martin Bigg, chairman of the Bristol Green Capital Partnership, said: "The award demonstrates that turning Bristol into a low-carbon city is central to our vision and by greening the city we are helping to make Bristol an even more attractive place to live, work, visit and study."
John Hirst, Destination Bristol's chief executive, added: "Bristol has developed a reputation for being a city that doesn't just think green, but acts green as well.
"We are already leading the way in the UK, so becoming European Green Capital is the natural next step, and helps to cement our place as a vibrant and forward-thinking city bringing us even more international acclaim. This great green achievement will undoubtedly help us to attract more visitors to enjoy our beautiful city."
The European Green Capital Award was set up in 2008 to reward cities that consistently achieve high environmental standards and are committed to further environmental improvement and sustainable development. The winning city must act as a role model and demonstrate a vision for the future that will inspire other cities to take similar action.