Social exclusion or social marginalisation is the social disadvantage and relegation to the fringe of society. It is a term that has been used widely in Europe and was first used in France in the late 20th century. It is used across disciplines including education, sociology, psychology, politics and economics.

Social exclusion is the process in which individuals are blocked from (or denied full access to) various rights, opportunities and resources that are normally available to members of a different group, and which are fundamental to social integration and observance of human rights within that particular group (e.g., housing, employment, healthcare, civic engagement, democratic participation, and due process).

Alienation or disenfranchisement resulting from social exclusion can be connected to a person's social class, race, skin color, religious affiliation, ethnic origin, educational status, childhood relationships, living standards, and or political opinions, and appearance. Such exclusionary forms of discrimination may also apply to disabled people, minorities, LGBTQ+ people, drug users, institutional care leavers, the elderly and the young. Anyone who appears to deviate in any way from perceived norms of a population may thereby become subject to coarse or subtle forms of social exclusion.

The outcome of social exclusion is that affected individuals or communities are prevented from participating fully in the economic, social, and political life of the society in which they live. This may result in resistance in the form of demonstrations, protests or lobbying from the excluded people.

The concept of social exclusion has led to the researcher's conclusion that in many European countries the impact of social disadvantages, that influence the well-being of all people, including with special needs, has an increasingly negative impact.

Most of the characteristics listed in this article are present together in studies of social exclusion, due to exclusion's multidimensionality.

Another way of articulating the definition of social exclusion is as follows:

Social exclusion is a multidimensional process of progressive social rupture, detaching groups and individuals from social relations and institutions and preventing them from full participation in the normal, normatively prescribed activities of the society in which they live.

In an alternative conceptualization, social exclusion theoretically emerges at the individual or group level on four correlated dimensions: insufficient access to social rights, material deprivation, limited social participation and a lack of normative integration. It is then regarded as the combined result of personal risk factors (age, gender, race); macro-societal changes (demographic, economic and labor market developments, technological innovation, the evolution of social norms); government legislation and social policy; and the actual behavior of businesses, administrative organisations and fellow citizens.