An international non-governmental organization (INGO) is an organization which is independent of government involvement and extends the concept of a non-governmental organization (NGO) to an international scope.

NGOs are independent of governments and can be seen as two types: advocacy NGOs, which aim to influence governments with a specific goal, and operational NGOs, which provide services. Examples of NGO mandates are environmental preservation, human rights promotions or the advancement of women. NGOs are typically not-for-profit, but receive funding from companies or membership fees. Many large INGOs have components of operational projects and advocacy initiatives working together within individual countries.

The technical term "international organizations" describes intergovernmental organizations (IGOs) and includes groups such as the United Nations or the International Labour Organization, which are formed by treaties among sovereign states. In contrast, INGOs are defined as "any internationally operating organization which is not established by inter-governmental agreement".

An INGO may be founded by private philanthropy, such as the Carnegie, Rockefeller, Gates and Ford Foundations, or as an adjunct to existing international organizations, such as the Catholic or Lutheran churches. A surge in INGOs for economic development occurred during World War II, some of which would later become large organizations like SOS Children's Villages, Oxfam, Catholic Relief Services, Care International and Lutheran World Relief. The number of INGOs grew from 6,000 in 1990 to 26,000 in 1999, and a 2013 report estimated about 40,000.

Except for incorporation under national laws, no current formal legal status exists for INGOs, which can lead to complications in international law.