Traditional knowledge (TK), indigenous knowledge (IK), folk knowledge, and local knowledge generally refers to knowledge systems embedded in the cultural traditions of regional, indigenous, or local communities.

Traditional knowledge includes types of knowledge about traditional technologies of areas such as subsistence (e.g. tools and techniques for hunting or agriculture), midwifery, ethnobotany and ecological knowledge, traditional medicine, celestial navigation, craft skills, ethnoastronomy, climate, and others. These systems of knowledge are generally based on accumulations of empirical observation of and interaction with the environment, transmitted orally across generations.

The World Intellectual Property Organization (WIPO) and the United Nations (UN) include traditional cultural expressions (TCE) in their respective definitions of indigenous knowledge. Traditional knowledge systems and cultural expressions exist in the forms of culture, stories, legends, folklore, rituals, songs, and laws, languages, songlines, dance, games, mythology, designs, visual art and architecture.

A report of the International Council for Science (ICSU) Study Group on Science and Traditional Knowledge characterises traditional knowledge as:

a cumulative body of knowledge, know-how, practices and representations maintained and developed by peoples with extended histories of interaction with the natural environment. These sophisticated sets of understandings, interpretations and meanings are part and parcel of a cultural complex that encompasses language, naming and classification systems, resource use practices, ritual, spirituality and worldview.

Traditional knowledge typically distinguishes one community from another. In some communities, traditional knowledge takes on personal and spiritual meanings. Traditional knowledge can also reflect a community's interests. Some communities depend on their traditional knowledge for survival. Traditional knowledge regarding the environment, such as taboos, proverbs and cosmological knowledge systems, may provide a conservation ethos for biodiversity preservation. This is particularly true of traditional environmental knowledge, which refers to a "particular form of place-based knowledge of the diversity and interactions among plant and animal species, landforms, watercourses, and other qualities of the biophysical environment in a given place". As an example of a society with a wealth of traditional ecological knowledge (TEK), the South American Kayapo people, have developed an extensive classification system of ecological zones of the Amazonian tropical savannah (i.e., campo / cerrado) to better manage the land.

Some social scientists conceptualise knowledge within a naturalistic framework and emphasize the gradation of recent knowledge into knowledge acquired over many generations. These accounts use terms like adaptively acquired knowledge, socially constructed knowledge, and other terms that emphasize the social aspects of knowledge. Local knowledge and traditional knowledge may be thought of as distinguished by the length of time they have existed, from decades to centuries or millennia.

On the other hand, indigenous and local communities themselves may perceive traditional knowledge very differently. The knowledge of indigenous and local communities is often embedded in a cosmology, and any distinction between "intangible" knowledge and physical things can become blurred. Indigenous peoples often say that indigenous knowledge is holistic, and cannot be meaningfully separated from the lands and resources available to them. Chamberlin (2003) writes of a Gitksan elder from British Columbia confronted by a government land-claim: "If this is your land," he asked, "where are your stories?"