Accounting for almost 3% of global CO₂ emissions, the maritime sector confronts a significant challenge in decarbonisation. This chapter examines the role of hydrogen and its derivatives in enabling this transition. It argues that while hydrogen is a crucial zero-carbon feedstock, its direct use as a marine fuel will remain niche due to profound challenges with volumetric energy density and storage. Instead, hydrogen-derived fuels, particularly green ammonia and e-methanol, are the most viable pathways for the sector’s decarbonisation at the moment. This chapter examines the technological readiness of fuel cells and combustion engines, the substantial infrastructure they require, and the key economic and policy measures needed to close the cost gap with conventional fuels. The analysis is framed by the evolving International Maritime Organization (IMO) climate framework—including the 2025 Net Zero Framework (NZF), whose adoption was postponed by a year amid political controversy—and the EU’s FuelEU Maritime regulation, which are set to fundamentally alter the economic landscape for marine fuels. The conclusion outlines a phased outlook, positioning direct hydrogen for short-sea applications and hydrogen-derived fuels as the long-term backbone for a sustainable maritime industry.