The Gulf of Guinea occupies a strategic position in global maritime trade and serves as a major source of petroleum resources, fisheries, and international shipping routes. Despite its economic significance, the region has become increasingly vulnerable to a wide range of transnational maritime crimes, including piracy, armed robbery at sea, illegal, unreported and unregulated (IUU) fishing, oil theft, drug trafficking, human trafficking, illicit arms trafficking, and marine pollution. These crimes pose serious threats to regional security, economic development, environmental sustainability, and the livelihoods of coastal communities. This study examines the nature and extent of transnational maritime crimes in the Gulf of Guinea and critically analyses the effectiveness of existing international, regional, and national legal frameworks designed to address these challenges. Particular attention is paid to the United Nations Convention on the Law of the Sea (UNCLOS), the United Nations Convention against Transnational Organized Crime (UNTOC), the Yaoundé Code of Conduct, the ECOWAS Integrated Maritime Strategy, ECCAS maritime initiatives, and selected national legal regimes. The study identifies major impediments to an effective regional response, including legal fragmentation, inadequate criminalization of maritime offences, weak maritime enforcement capabilities, corruption, poor information sharing, and ineffective regional coordination mechanisms. The paper argues that the transnational nature of maritime crimes necessitates a harmonized legal and institutional approach among Gulf of Guinea states. It concludes by proposing comprehensive legal reforms, enhanced intelligence sharing, strengthened operational cooperation, and sustainable funding mechanisms as essential measures for achieving long-term maritime security and stability in the region.