This article traces the origins of US-China strategic competition in maritime security by analyzing the securitization of China’s aggressive actions in the South China Sea. Around 2010, China accelerated its naval buildup and expansion into the South China Sea, resulting in conflicts with neighboring East Asian countries. The South China Sea has been considered a region where the US and China could collide, as one seeks to expand its influence while the other seeks to contain it. Consequently, this article’s analysis has significant implications for understanding the beginning of the US-China strategic competition in maritime security. In particular, the article draws on securitization theory and analyzes how the “China threat” discourse in the US has securitized China’s actions in the South China Sea.