Mature industries have played and still play a crucial role in national and world economies. To survive and retain competitiveness, they need to innovate, as innovation is the driver of economics growth and industrial transformation. However, existing research does not provide sufficient explanation of how innovation in mature industries can be enabled based on resources and internal development logic of those industries, i.e. endogenously. Some previous studies focused on incremental innovation patterns, which led to an underestimation of innovation potential of mature industries. Other studies acknowledged a high innovation potential of mature industries, but failed to explain how, through what mechanisms, industry-endogenous logic can bring about major innovations.Therefore, the purpose of this thesis is to systematically address, explain and conceptualize industry-endogenous innovation and its driving mechanisms in mature industries. To achieve this purpose, three main issues are addressed. First, the thesis investigates and conceptualizes the notion of industry endogenous innovation mechanisms based on the path dependency theory. Second, the thesis addresses strategic choices and actions by established companies that are rooted in the industry endogenous mechanisms and result in highly innovative outcomes. Third, the thesis systematically analyses different aspects of radicalness of innovations resulting from industry endogenous mechanisms.The thesis represents a qualitative, embedded case study with two main industry cases, i.e. the global lighting industry and the Swedish pulp and paper industry. The lighting industry and its subcases in the form of specific lighting technologies have been studied via the analysis of patents of leading lighting manufacturers, archival and secondary data sources as well as interviews with different types of actors in the industry. The pulp and paper industry and its sub-cases in the form of innovation initiatives have been studied with the help of interviews with leading manufacturers and research institutes, as well the analysis of annual reports and secondary data sources. The outcomes of the study are presented in the form of the thesis cover paper and five appended papers.The results show that innovations of any magnitude can be endogenously developed in mature industries. At the industry level, endogenous innovation is driven by innovation mechanisms that can be conceptualized as reactive sequences and self-reinforcing mechanisms. At the level of individual companies, the exploitation strategy corresponds to the logic of endogenous innovation mechanisms by enabling highly innovative outcomes and building on a wide range of resources available in the industry. The endogenous character of innovation mechanisms imposes certain limitations on the radicalness of the outcomes in the form of trade-offs in terms of how many and what particular aspects can be radically new at once.With these results, the thesis contributes to a more balanced overall understanding of in...