Mixed-use development is the use of a building, set of buildings, or neighborhood for more than one purpose. Since the 1920s, zoning in some countries has required uses to be separated. However, when jobs, housing, and commercial activities are located close together, a community's transportation options increase. In addition, mixed-use developments often have higher property values. Often located in existing urban areas or as part of a new town center, mixed-use development provides a range of commercial and residential unit sizes and options. In planning zone terms, this can mean some combination of residential, commercial, industrial, office, institutional, or other land uses. The concept of "mixed-use" as a discrete zone is predicated on the relatively recent practice of single-use zoning whereby different uses in different places are set by legislative mandate.

Throughout most of human history, the majority of human settlements developed as mixed-use environments. Walking was the primary way that people and goods were moved about, sometimes assisted by animals such as horses or cattle. Most people dwelt in buildings that were places of work as well as domestic life, and made things or sold things from their own homes. Most buildings were not divided into discrete functions on a room by room basis, and most neighborhoods contained a diversity of uses, even if some districts developed a predominance of certain uses, such as metalworkers, or textiles or footwear due to the socio-economic benefits of propinquity. People lived at very high densities because the amount of space required for daily living and movement between different activities was determined by walkability and the scale of the human body. This was particularly true in cities, and the ground floor of buildings was often devoted to some sort of commercial or productive use, with living space upstairs.