Capitalism has required the function of the entrepreneurs, people who use creativity, understood as the ability to solve problems and put innovation into practice. Firms can be social, public, and private; in this last case, the creation of an enterprising company involves new products, new production methods, the opening of new markets, the development of new sources of raw materials and inputs, and the creation of new market structures in the industry. This chapter is a bibliographical review of the theories of entrepreneurship from economics, sociology, psychology, and management aiming to contribute to the construction of a definition of entrepreneurship and entrepreneur that can be accepted by scholars in this field.