Affirmative action, also known as positive action or positive discrimination, involves sets of policies and practices within a government or organization seeking to include particular groups based on their gender, race, sexuality, creed or nationality in areas in which such groups are underrepresented — such as education and employment. Historically and internationally, support for affirmative action has sought to achieve goals such as bridging inequalities in employment and pay, increasing access to education, promoting diversity, and redressing apparent past wrongs, harms, or hindrances.

The nature of affirmative-action policies varies from region to region and exists on a spectrum from a hard quota to merely targeting encouragement for increased participation. Some countries use a quota system, reserving a certain percentage of government jobs, political positions, and school vacancies for members of a certain group; an example of this is the reservation system in India.

In some other jurisdictions where quotas are not used, minority-group members are given preference or special consideration in selection processes. In the United States, affirmative action in employment and education has been the subject of legal and political controversy. In 2003, the Supreme Court of the United States, in Grutter v. Bollinger, held that the University of Michigan Law School could consider race as a plus-factor when evaluating applicants holistically and maintained the prohibition on the use of quotas.

In the United Kingdom, hiring someone simply because of their protected-group status, without regard to their performance, is illegal. However, the law in the United Kingdom does allow for membership in a protected and disadvantaged group to be considered in hiring and promotion when the group is under-represented in a given area and if the candidates are of equal merit (in which case membership in a disadvantaged group can become a "tie-breaker"). An alternative approach, common in the United Kingdom and elsewhere in Europe, is positive action. Under this approach, the focus tends to be on ensuring equal opportunity and, for example, targeted advertising campaigns to encourage ethnic minority candidates to join police forces. This is often described as being "color blind", although the social viability of that concept is heavily contested by certain elements in the United States.

In the United States, affirmative action is controversial and public opinion on the subject is divided. Supporters of affirmative action argue that it promotes equality and representation for groups which are socio-economically disadvantaged or have faced historical discrimination or oppression. Opponents of affirmative action have argued that it is a form of reverse discrimination, that it tends to benefit the most privileged within minority groups at the expense of the least fortunate within majority groups, or that—when applied to universities—it can hinder minority students by placing them in courses too difficult for them.