Cultural diversity is the quality of diverse or different cultures, as opposed to monoculture. It has a variety of meanings in different contexts, sometimes applying to cultural products like art works in museums or entertainment available online, and sometimes applying to the variety of human cultures or traditions in a specific region, or in the world as a whole. It can also refer to the inclusion of different cultural perspectives in an organization or society.

Cultural diversity can be affected by political factors such as censorship or the protection of the rights of artists, and by economic factors such as free trade or protectionism in the market for cultural goods. Since the middle of the 20th century, there has been a concerted international effort to protect cultural diversity, involving the United Nations Educational, Scientific and Cultural Organization (UNESCO) and its member states. This involves action at international, national, and local levels. Cultural diversity can also be promoted by individual citizens in the ways they choose to express or experience culture.

In the context of national and international efforts to promote or preserve cultural diversity, the term applies to five overlapping domains:

Of these five, the economic meaning has come to dominate in international negotiations. Nations have principally looked to protect cultural diversity by strengthening the ability of their domestic cultural industries to sell goods or services. Since the 1990s, UNESCO has mainly used "cultural diversity" for the international aspects of diversity, preferring the term "cultural pluralism" for diversity within a country.

Governments and international bodies use "cultural diversity" in both a broad and a narrow sense. The broad meaning takes its inspiration from anthropology. It includes lifestyles, value systems, traditions, and beliefs in addition to creative works. It emphasises an ongoing process of interaction and dialogue between cultures. This meaning has been promoted to the international community by UNESCO, since the 2001 Universal Declaration on Cultural Diversity. In practice, governments use a narrower, more traditional, meaning that focuses on the economic domain mentioned above.

In the international legal context, cultural diversity has been described as analogous to biodiversity. The General Conference of UNESCO took this position in 2001, asserting in Article 1 of the Universal Declaration on Cultural Diversity that "cultural diversity is as necessary for humankind as biodiversity is for nature." The authors John Cavanagh and Jerry Mander took this analogy further, describing cultural diversity as "a sort of cultural gene pool to spur innovation toward ever higher levels of social, intellectual and spiritual accomplishment."

Cultural diversity is difficult to quantify. One measure of diversity is the number of identifiable cultures. The United Nations Department of Economic and Social Affairs reports that, although their numbers are relatively small, indigenous peoples account for 5,000 distinct cultures and thus the majority of the world's cultural diversity.

Another aspect of cultural diversity is measured by counting the number of languages spoken in a region or in the world as a whole. By this measure, the world's cultural diversity is rapidly declining. Research carried out in the 1990s by David Crystal suggested that at that time, on average, one language was falling into disuse every two weeks. He calculated that if that rate of the language death were to continue, then by the year 2100, more than 90% of the languages currently spoken in the world will have gone extinct.