As the process of urbanisation ramps up around the world, the question, “Which is the cleanest city in the world?” has become more important than in the past.
Clean cities not only provide better health to their residents but also attract tourists, stimulate economic growth, and set standards for sustainable practices going forward.
Did you know? Copenhagen, in 2025, was named the world’s happiest city, making it a clear indicator of the connection between a clean setting and a high quality of life.
In this in-depth report, we will look at the best 10 clean cities in the world, including Copenhagen’s carbon-neutral projects and Singapore’s waste management innovations.
This comprehensive guide will look at the environmental policies, cultural practices, and the latest technologies that make these urban centres global leaders in sustainability and quality of life.
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How to Rank the Cleanest Cities in the World?
Determining the cleanest city in the world is a task that requires a comprehensive evaluation framework. International organisations like the Environmental Performance Index, the Mercer Quality of Living Survey, and various UN sustainability reports serve as the base for these rankings.
These studies look at air quality indices (AQI), received from WHO data, waste management performance, recycling rates, water quality standards, and green infrastructure growth. Also, they look at public perception research, policy for the environment’s effectiveness, and sustainability projects.
Top 10 Cleanest Cities in the World
1. Copenhagen, Denmark
The Danish capital’s report card is ranking highly because it has set out to be carbon neutral by 2025 and has implemented very innovative waste-to-energy programs.
Copenhagen’s district heating network, which is powered by waste incineration, serves 98% of the city. Also, 62% of residents reported being daily cyclists, which in turn reduces emissions.
The city reports a 50% waste recycling rate, which is very high. At the same time, it is noted for some of the cleanest air in Europe, well below WHO guidelines.
Beyond the impressive enviro stats, in 2025, Copenhagen was named the happiest city in the world, which puts into play that environmental quality improves the quality of life and health of its citizens.
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2. Singapore
Singapore is the prime example in Asia of the cleanest city in the world and also grows in a tropical environment through smart urban planning.
This city-state has strict environmental rules in place, which include heavy fines for littering and very thorough waste sorting systems.
Singapore’s NEWater initiative cleanses 40% of the water the nation uses. The city reports 47% green space despite it being such a dense area.
The government’s “City in a Garden” concept has brought in vertical gardens, rooftop farming, and incorporated nature into the urban design. The air quality is extremely good with the use of advanced monitoring systems. They recycle 99% of our waste through incineration and recycling programs.
3. Calgary, Canada
The Alberta city is a leader in waste diversion, achieving a rate of 70% in recycling and composting, the highest globally.
This only goes on to show that a city can achieve the title of cleanest city in the world through community involvement and progressive policies.
Calgary is home to the Green Line public transit project and a large-scale pathway, which in turn promotes sustainable transport options. The city’s river system is exceptionally well, credited to strict watershed protection.
Also, the city is committed to renewable energy, helping it report some of the cleanest air in Canada. Calgary does an excellent job with snow management and street cleaning, helping it uphold very high annual cleanliness standards, putting it on par with the best global cities.
4. Helsinki, Finland
Helsinki weaves into its urban fabric a design, a part of the Nordic environmental movement and innovative technology, putting it in the running for the title of cleanest city in the world.
A leader in the implementation of a very efficient district heating system runs on renewable resources, which today serves 90% of its buildings.
The city has an extensive public transport system which includes metros, trams and buses that report 95% rider satisfaction and at the same time emits fewer emissions.
In Helsinki, there’s a 42% household waste recycling rate. This is made possible by innovative underground waste collection systems, which keep the streets very clean. The Baltic Sea gives it excellent air quality, putting it among the cleanest urban environments in all of Europe.
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5. Auckland, New Zealand
Auckland uses its island setting and environmental heritage to become the cleanest city in the world.
New Zealand’s largest city has access to constant sea breezes, producing excellent air quality and some of the world’s lowest pollution levels.
The city is home to a 60% efficient recycling program and very strict building codes for sustainable development. In Auckland, there are extensive regional park ecosystems which cover 40,000 hectares and give green cover to the metropolitan area.
Also, the city is on track to become carbon neutral by 2050, which includes large-scale investment in electric public transport and renewable energy infrastructure.
6. Adelaide, Australia
Adelaide is the prime example of what mid-sized cities can do to become the cleanest city in the world via innovative water management and urban forestry.
South Australia’s capital has the world’s most advanced water recycling system that treats and reuses 35% of metropolitan wastewater.
In the past two decades, the city has been working on its "20-Year Plan for Greater Adelaide" and has planted 3 million trees since 2003.
They have a Mediterranean climate, which supports year-round outdoor activities, and at the same time, excellent air quality.
The extensive curbside recycling program achieved 65% in terms of waste diversion. The city centre is also made pedestrian-friendly, which in turn reduces vehicle emissions.
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7. Tokyo, Japan
Tokyo, a giant city, proves that it can be the cleanest city in the world through cultural discipline and technological innovation. In Japan’s capital, waste from 14 million residents is managed through very detailed sorting, achieving 23% recycling.
Tokyo maintains extremely clean public spaces in a highly dense environment, made possible by strong social norms and comprehensive street cleaning services. Also, they have an extensive rail network transporting 40 million passengers every day with little environmental impact.
The good air quality is a result of strict emissions standards. In terms of sustainability, Tokyo has set out ambitious targets for renewable energy and also has creative urban cooling solutions.
8. Zurich, Switzerland
Zurich is known for its Swiss efficiency, which it applies to the environment to maintain its position as the cleanest city in the world.
Switzerland’s financial centre has an excellent public transport system, 95% of which runs on time, encouraging residents to do away with private cars. The city also achieves 70% recycling via extensive collection programs and education of its citizens.
Zurich, which sits by Lake Zurich, has natural water filtration and recreational spaces at its disposal. It has also put in place strict building energy codes, producing minimal emissions. The city's commitment to becoming fossil fuel-free by 2050 includes district heating networks and renewable energy mandates for new construction.
9. Oslo, Norway
Oslo shows how Nordic cities meet the cleanest city in the world criteria using renewable energy leadership and innovative transport initiatives. Norway's capital operates entirely on renewable electricity, with 98% of power generation from hydroelectric sources.
The city's ambitious electric vehicle adoption program has resulted in 80% of new car sales being electric, while comprehensive charging infrastructure supports this transition. Oslo's district heating system serves 80% of buildings using renewable sources and waste heat recovery.
The 2030 carbon-free vision of the city is backed by large urban forestry initiatives and cutting-edge stormwater management that keeps waterways in pristine condition.
10. Honolulu, USA
Honolulu uses its Pacific island location and Polynesian conservation ethic to gain the title of the cleanest city in the world. The capital of Hawaii enjoys a steady trade wind climate that keeps its air quality superior and natural cooling systems.
The city's commitment to renewable energy aims for 100% clean electricity by 2045, while comprehensive recycling programs address the unique challenges of island waste management.
Honolulu's extensive beach cleaning programs and coral reef protection initiatives maintain pristine coastal environments that attract millions of visitors annually.
The city's integration of traditional Hawaiian environmental practices with modern sustainability technology creates a unique model for tropical urban cleanliness.
Setting Global Standards for Urban Excellence
These ten cities demonstrate that becoming a city of urban excellence needs holistic strategies integrating technology, policy, and culture.
Whether it is Copenhagen's vision to be carbon neutral, Singapore's water revolution, or Toronto's innovative climate plan, all show that environmental excellence augments economic success and citizen well-being.
With urbanisation increasingly spreading around the world, these cities are crucial blueprints for developing healthier, more resilient communities for generations to come.
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