Particularly in the 21st century, the importance of IOs has remarkably increased due to the rapid development of interdependent structures in the world order as a result of the globalization process. It is in this context where IOs emerge as vital actors that involve in any type of political, economic, and social challenges that this century faces

Because the early international system had been mainly dominated by European nation states, first IOs emerged in the 19th century in Europe. The Congress of Vienna (1815) created a more convenient atmosphere for the development of IOs.

The increase and diversification of IOs in international politics is closely related to globalization which emerged as a result of the rapid changes of the 20th century. Diez and his colleagues describe globalization as a “catch-all” concept that refers to “the widespread perception of the world as merging into a shared global economic and social space, a process caused by information technologies and an increased degree of interdependency”

The main reason why there was not any successful attempt at establishing international organizations prior to the 19th century is “that these organizations had to await the creation of a relatively stable system of sovereign states in Europe.” Furthermore, political, economic, and social changes in the 19th century led states to acknowledge some common problems and recognize new mechanisms to regulate their relations.

It was only after the First World War that modern IOs started to emerge. Archer considers the Paris Peace Conference of 1919 as the starting point of contemporary IOs. After the Conference, the League of Nations and International Labour Organization (ILO) were established as the leading modern IOs.

It is generally accepted that states are no longer the only actor of international politics and international law. Today IGOs, INGOs, MNCs, individuals, and sub-state groups are also major actors.

Over the years new IOs have been established. For one thing, this process led to the diversification of international actors. Besides states, IGOs, NGOs, international regimes, citizens’ movements, and global mass media have emerged as new types of actors. For another, this has led to the erosion of states’ authority. From the local level to the international level, the authority of non-state actors such as IGOs and NGOs have increased. The emergence of new international actors has forced states to take their decisions in more complicated processes.

The growing roles of IOs and the increasing interdependence among states showed the importance of the concept of governance for understanding complex international affairs. Particularly, the end of the Cold War marked the beginning of the governance studies.

Governance has emerged as a concept to describe the activities of both formal and informal processes and institutions. Governance differs from government, which only reflects a formal structure (Keohane and Nye, 2002: 202). Government is a formal institution that has legitimate coercive powers and can enforce its decisions on its citizens. The actual difference between government and governance can be observed in political processes.

Evans and Newham identify the scope of global governance as follows: “Global governance should not be confused with World government, which implies a singular or unitary authority. Nor does it focus exclusively on intergovernmental relationships. Rather it involves the participation of non-governmental organizations (NGOs), multinational corporations (MNCs), citizens’ movements, the global mass media and the global capital markets.

Having defined IOs and global governance, we can now focus on their classification. In the literature, IOs are categorized according to three criteria: membership, aims and activities, and structure.

Intergovernmental organizations are divided into three categories:

Another type of IOs is called transnational organizations (TNOs). The concept of transnational organization refers to the institutionalization of global interactions under a formal and permanent structure through an agreement among more than two participants of which at least one is a non-state actor.

TNOs are divided into three types: genuine INGOs, hybrid NGOs, and trans-governmental organizations (TGOs). INGOs are organizations that only consist of non-governmental actors. The International Olympic Committee is a telling example of INGOs. International non-governmental organizations that consist of both governmental members and non-governmental members are characterized as hybrid INGOs. There is also a new trend that IGOs involve civil society representation through the participation of INGOs in their meetings. The UN’s global summits in environment issues clearly illustrate this point. Trans-governmental organizations, on the other hand, refer to the networks of cooperation between governmental actors that are not part of central foreign policy organs. The International Union of Local Authorities (IULA), the Interpol, or the Inter-Parliamentary Union are some examples of TGOs.

If the members of an organization belong to a specific geographical region, this kind of organization is classified as a regional organization. The most notable examples of regional organizations are the European Union (EU), the African Union (AU) and the Organization of American States (OAS).

The founding document of an organization defines its main aims. These aims can vary based on the subject matter of the organization. For example, the main purpose of the UN is defined in the Preamble of the UN Charter as maintaining international peace and security. Thereby, its overarching aim of maintaining international peace and security also determines the nature of its activities in different issue areas.

An international organization may have various organs mandated with specific functions. These organs can be interstate organs, organs of international officials, parliamentary organs, organs of the representative of interest groups of economic and social life, and organs of mixed membership.

Archer identifies nine main functions of IO. These are: articulation and aggregation, norm-setting, recruitment, socialization, rulemaking, rule application, rule adjudication, information, and operation

The main theoretical classification on the role of international relations is structured around: traditional realism, liberalism, Marxism along with constructivism, feminism, the green theory, and other integration theories.

Realism considers the concept of power as the ability to change and adjust the behavior of others in an anticipated way. Presuming that the state behavior is mainly shaped by the dynamics of power and security in international relations, it is hypothesized that states can maximize their self-interests by providing their own security and preserving (and even increasing) their own power

Hans Morgenthau also focuses on the structure of interstate relations and regards IOs as “interstate institutions”. From the traditional realist perspective, Morgenthau argues that:

affairs. Marxism criticizes capitalism as the main mode of production on the grounds that it causes inequalities among nation states and thus destabilizes the world order and increases the possibility of a conflict among states. Marxism regards IOs as tools and/or influence mechanisms of capitalism that widen the gap between the developed nations and the developing/ underdeveloped nations.

As one of the critical theories of international relations, feminism focuses on the role of gender and gender politics in international affairs. Feminism discusses women’s possible role in, and contribution to, the decision-making and policy-making processes within IOs with regard to important issues of international affairs and global governance. Feminism holds that gender matters for creating and changing institutional structures and that women should play an equal role as men in this process.

The environmental issues are no longer considered within the scope of nation states. Rather, these issues expanded and many new actors participated in managing them, including “networks of experts, environmentalist organizations and multinational corporations as well as new agencies set up by governments”.

This theoretical approach suggests that today IOs play a significant role in the decision-making mechanisms that deal with environmental issues and develop “legally binding” policies negotiated and agreed upon by nation states and non-state entities. In fact, IOs help to strengthen the idea of global governance on environmental issues by reconciling processes of rule-making and rule implementation that takes place at different levels of governance, i.e. sub-national, national, supranational, and international

Integration theories are considered to be useful for several reasons. First, they help us understand the rationale behind integration processes and the effects of such processes in terms of costs and benefits. The connection between the rationale and outcomes of integration processes is thus considered to be useful for making projections on future integration initiatives and for the behavioral analysis of states and institutions. Second, integration theories shed light on the functioning of formal institutional structures, because they reflect upon the credibility and legitimacy of these structures especially with regard to decision making on behalf of the nation states that participate in the integration process. Third, it is argued that these theories provide a clear understanding of how institutions work because they blend the facts and empirical research with underlying theoretical assumptions on inter-state relations and policy-making processes

Neofunctionalism, a theory of regional integration, was developed in the 1960s and 1970s as a “moderate conceptual tool” for assessing the European integration process. Neofunctionalism expands the notions of functionalism by combining the “functionalist mechanisms” with “federalist goals,” devoting extensive self-sufficiency to “supranational” institutions.

Regionalism is a theory or practice of the integration process, which coordinates social, economic, and political activities within a specific geographical location embodying a number of states. Regionalism is considered as a supplement of, rather than an alternative to, the universal and global integration process.