In cultural anthropology and cultural geography, cultural diffusion, as conceptualized by Leo Frobenius in his 1897/98 publication "Der westafrikanische Kulturkreis", is the spread of cultural items—such as ideas, styles, art, religions, technologies, languages—between individuals, whether within a single culture or from one culture to another. It is distinct from the diffusion of innovations within a specific culture. Examples of cultural diffusion include the spread of the war chariot and of iron smelting in ancient times, and the use of automobiles and Western business suits in the 20th century.

Five major types of cultural diffusion have been defined:

Inter-cultural diffusion can happen in many ways. Migrating populations will carry their culture with them. Ideas can be carried by trans-cultural visitors, such as merchants, explorers, soldiers, diplomats, enslaved people, and hired artisans. Technology diffusion has often occurred by one society luring skilled scientists or workers by payments or another inducement. Trans-cultural marriages between two neighboring or interspersed cultures have also contributed. Among literate societies, diffusion can occur through letters, books, and, in modern times, through electronic media.

There are three categories of diffusion mechanisms:

Direct diffusion was common in ancient times when small groups of humans lived in adjoining settlements. Indirect diffusion is common in today's world because of the mass media and the invention of the Internet. Also of interest is the work of American historian and critic Daniel J. Boorstin in his book The Discoverers, in which he provides a historical perspective on the role of explorers in the diffusion of innovations between civilizations.

The many models that have been proposed for inter-cultural diffusion are:

A concept that has often been mentioned in this regard, which may be framed in the evolutionary diffusionism model, is that of "an idea whose time has come"—whereby a new cultural item appears almost simultaneously and independently in several widely separated places, after certain prerequisite items have diffused across the respective communities. This concept was invoked with regard to the independent development of calculus by Newton and Leibnitz, and the inventions of the airplane and of the electronic computer.

Hyperdiffusionists deny that parallel evolution or independent invention took place to any great extent throughout history; they claim that all major inventions and all cultures can be traced back to a single culture.