Entrepreneurs play a key role in the commercialization of new technologies and products: this chapter explores their sources of comparative advantage vis-à-vis large incumbent organizations which often have deeper pockets and established distribution systems. In general, innovative entrepreneurs engage in a strategic game with incumbents. Models of this kind can explain the counter-intuitive finding that small-scale independent entrepreneurs often produce the most radical innovations while incumbents settle for more incremental improvements to processes and products. Organizational limitations of existing firms, as well as agency costs and learning trajectories can also explain why some firms spawn spinoffs. These spinoffs can drain value from incumbents and nurture sharp new competitive threats to their very existence. A rich body of theory and evidence is discussed which elucidates these ideas. The chapter closes with a brief discussion of inventors as well as academic entrepreneurs who commercialize new ideas developed in universities.