Abstract: Policy communities throughout the world tend to agree that in recent years China has become more assertive in its maritime disputes with neighbouring countries. However, scholars vehemently disagree about the underlying motivations for such a change, whether structural factors, China’s external pressures, or growing overseas interests. This article argues that existing analysis runs the risk of dismissing the embedded logic of domestic legitimacy as the single most important explanation. China’s maritime strategy has almost always served the goal of legitimisation in consistence with the Party’s central enterprises, be they survival, modernisation, or political influence/power. The rise of naval nationalism from within has pushed the central leadership to respond with determination for the sake of maintaining credibility as ‘national saviour and protector’. More importantly, in view of the bureaucratic fragmentation in China’s maritime governance, new policy actors can forward their own interests by appealing to nationalist sentiments, and to the Party’s new central task of projecting political power. Our case studies on Sansha City, the Diaoyu/Senkaku Islands, and the Haiyang Shiyou 981 Drilling Rig bring in supportive evidence. Specifically, they demonstrate that all extant explanations may indeed influence China’s maritime strategy, but mostly through their impact on domestic legitimacy. Based on our legitimacy thesis, it can be predicted that, if the central leadership manages to consolidate its domestic legitimacy, China will assume a more moderate, cooperative, and constructive attitude towards maritime disputes. Full text available here.