This chapter undertakes a comprehensive exploration of the evolution of the Korea Fair Trade Commission’s (KFTC) enforcement practices concerning the abuse of market dominance. It begins by tracing the institutional and procedural development of the KFTC’s approach, situating it within the broader context of competition policy. The analysis then turns to the theoretical underpinnings of market definition and the assessment of market power—conceptual cornerstones that frame the inquiry into exclusionary and exploitative conduct. Subsequently, the discussion engages with the economic rationale behind various forms of potentially abusive behavior, drawing on foundational principles from industrial organization. Particular attention is given to practices such as exclusive dealing, tying and bundling, predatory pricing, price discrimination, refusal to deal, and other strategies with foreclosure effects. These are examined not only in terms of their competitive implications but also through the lens of allocative and dynamic efficiency. The chapter concludes by examining several significant cases of market dominance abuse in Korea, including: Posco’s refusal to trade in 2001, Microsoft’s tying practices in 2006, NHN (Naver)’s advertising restrictions in online video content in 2008, Intel’s conditional rebates in 2008, Qualcomm’s discriminatory royalties in 2010, LGU Plus’ margin squeeze in 2015, Qualcomm’s licensing and modem chipset supply business model in 2017, Siemens’ maintenance software fees in 2018, Naver—Shopping’s self-preferencing in 2021, and Google’s antifragmentation agreement.