City diplomacy

Definition

City diplomacy describes the practice of municipalities engaging directly on the international stage to address shared urban issues. Mayors, city councils, and local officials act as diplomatic agents, forming networks and partnerships to collaborate on challenges such as climate change, public health, and economic growth.

This form of international relations operates parallel to, and often in support of, national foreign policy. It allows cities to exchange knowledge, attract investment, and advocate for their interests within global governance frameworks. Rather than replacing traditional state-to-state relations, city diplomacy provides a pragmatic channel for problem-solving, grounded in the tangible needs of urban populations.

It is a direct response to the reality that many of the world’s most pressing problems are concentrated in and must be solved by cities. This approach empowers local leaders to craft international solutions for local issues, making them key actors in global affairs.

Relevance

As urbanisation continues globally, cities have become critical centres of economic power, innovation, and population. Over half of the world’s population lives in urban areas, making cities the frontline for tackling global challenges. Problems like climate change, pandemics, and social inequality manifest acutely in cities, demanding immediate and practical solutions. City governments can often act more nimbly than their national counterparts, free from the complex geopolitics that can stall progress at the state level. They serve as laboratories for policy innovation, testing solutions in transport, housing, and sustainability that can later be adopted elsewhere.

Economically, cities compete to attract talent, tourism, and investment, making international engagement essential for prosperity. Mayors leading trade missions to other countries is a common practice aimed at securing business deals and creating local jobs. Politically, a unified voice from the world’s major cities can influence global agendas and encourage national governments to make more ambitious commitments, particularly on environmental issues. City diplomacy is therefore not just a municipal activity; it is a vital component of effective global governance. This direct engagement connects local action to worldwide challenges, ensuring that the perspectives of billions of urban dwellers are represented on the international stage.

Methods and approaches

Cities conduct their international relations through a variety of methods. A primary mechanism is participation in transnational city networks, such as C40 Cities or United Cities and Local Governments (UCLG). These platforms facilitate knowledge sharing, policy coordination, and collective advocacy on the global stage. Bilateral agreements remain a common tool. The traditional ‘sister city’ relationship, once largely symbolic, has evolved to encompass concrete collaborations on trade, technology, and cultural projects.

Mayors and city delegations often undertake economic promotion missions abroad to secure foreign direct investment and promote local industries. Cities also engage in direct lobbying, seeking to influence the decisions of international organisations like the United Nations and regional bodies such as the European Union. Through these efforts, they ensure that urban priorities are included in global policy frameworks.

Informal channels are equally important. Hosting major international events, from the Olympic Games to cultural festivals, provides cities with opportunities to project their identity and build soft power. These diverse approaches allow cities to tailor their diplomatic activities to specific goals, whether securing economic benefits or contributing to global policy debates. They combine formal institutional links with informal person-to-person connections to build robust international relationships.

Geographical scope

City diplomacy operates across multiple geographical scales, transcending traditional state-centric boundaries. In bilateral relations, two cities from different countries establish direct partnerships to work on specific projects, such as a technology transfer agreement between Seoul and Barcelona.

At a regional level, networks like Eurocities or the US Conference of Mayors allow cities within a geographical area to coordinate policies and advocate for their interests with regional authorities. This regional cooperation helps address cross-border issues like transportation and air quality.

The most visible arena is the multilateral forum. While cities are not formal members of organisations like the United Nations, they increasingly participate in and influence global summits on issues like climate (COPs) and urban development (Habitat III). They also create their own global venues, with networks like UCLG holding world congresses that function as parallel diplomatic summits for local leaders. These activities demonstrate that city diplomacy is not confined to one location but takes place wherever urban leaders can connect to share solutions and assert their collective influence.

Historical development

While ancient city-states like Athens and Venice engaged in foreign relations for centuries, modern city diplomacy has distinct origins. Its initial form appeared in the post-World War II era with the ‘town twinning’ or sister city movement. Primarily driven by a desire for peace and reconciliation, especially between French and German cities, these partnerships were initially focused on cultural exchange and rebuilding trust at a grassroots level. The practice expanded during the Cold War as a means of citizen-to-citizen connection across the Iron Curtain. 

A significant shift occurred from the 1980s onward with the rise of globalisation and decentralisation. As national governments devolved powers, cities gained more autonomy and began to pursue their international interests more assertively, focusing on economic development and competitiveness. The 1992 Rio Earth Summit was a key moment, formally recognising local authorities as important actors in sustainable development. This acknowledgement catalysed the formation of influential city networks dedicated to environmental issues. This turning point helped move city diplomacy from a symbolic gesture of peace to a pragmatic tool for solving pressing global problems, giving cities a formal role in shaping international environmental policy.

Actors

he primary actors in city diplomacy are mayors and their municipal administrations. Mayors often serve as the public face of a city on the world stage, leading international delegations and negotiating partnerships. They are supported by specialised international relations units within their city halls.

Transnational city networks are crucial institutional actors. Organisations like C40 Cities (climate), ICLEI – Local Governments for Sustainability (sustainability), and UCLG (local government advocacy) provide the platforms, resources, and collective voice that amplify the influence of individual cities.

International organisations, including the World Bank and various UN agencies like UN-Habitat, now actively engage with cities as partners in development projects. Beyond the public sector, civil society groups and non-governmental organisations often collaborate with city governments on international campaigns. The private sector is also a key participant, with corporations partnering with cities on economic missions and sustainable urban development initiatives. These different actors work together to advance a city’s international agenda.

Examples

The Role of Cities in the 2015 Paris Agreement

Just days before the final negotiations of the COP21 climate summit in 2015, Mayor Anne Hidalgo of Paris convened over 1,000 mayors and local leaders at the Paris City Hall for the Climate Summit for Local Leaders. This gathering was not merely symbolic; it was a powerful political statement. The assembled leaders committed their cities to ambitious climate targets, showcasing that significant emissions reductions were achievable at the local level. This demonstration of readiness created crucial momentum and applied pressure on national negotiators to adopt a more ambitious global treaty. The collective pledge helped counter arguments that strong climate action was unfeasible. The event solidified the role of networks like C40 Cities as key players in global climate governance, proving that city-level action could directly influence the outcome of international state-level agreements.

Barcelona’s “City of Refuge“ Plan

In 2015, at the height of the Syrian refugee crisis in Europe, Barcelona’s mayor, Ada Colau, launched the ‘Ciutat Refugi‘ (City of Refuge) plan. This initiative positioned Barcelona as a city willing to welcome and integrate refugees, often in direct contrast to the more hesitant stance of the Spanish national government. The city administration created a detailed plan to receive asylum seekers, mobilised citizen volunteers, and publicly called on the central government to honour its refugee quotas. Although the city’s capacity was limited by national immigration laws, the move was a significant act of political and humanitarian diplomacy. It sent a clear message on the international stage about Barcelona’s values and inspired similar movements in other European cities, forming an informal network of solidarity.

The Global Covenant of Mayors for Climate & Energy

The Global Covenant of Mayors for Climate & Energy represents the largest global alliance for city climate leadership, bringing together over 10,000 cities across six continents. Formed through the merger of the EU’s Covenant of Mayors and the UN’s Compact of Mayors, it provides a framework for cities to set ambitious targets, measure their progress transparently, and share solutions. Member cities voluntarily commit to combating climate change. This initiative is a prime example of institutionalised city diplomacy. It standardises how cities report climate data, allowing for a credible global assessment of their collective impact and giving them a stronger, unified voice in international climate negotiations.