Maritime transport accounts for 90% of global trade. Recent data indicates that maritime transport grew by 2.4% in 2023 and is projected to grow at an annual rate of 2.1% over the next 5 years. The global maritime fleet comprises 105,493 ships above 100 gross tonnages, the majority of which use low-quality fossil-based fuels. Heavy fuel oil constitutes 72% of these fuels, marine diesel oil 26%, and only 2% is a low-carbon fossil fuel, specifically LNG. Along with the emission studies of the International Maritime Organization (IMO), there are considerable low or zero-carbon alternative fuels for maritime transport beyond LNG. One promising alternative is ammonia, which boasts a zero-carbon structure, easy storage capabilities, and an energy density comparable to other alternative fuels like methanol. Utilizing ammonia could help achieve the IMO’s 2050 net-zero target. However, ammonia’s unique properties must be carefully managed. As a toxic and corrosive substance, ammonia poses significant risks to the marine ecosystem if spilled. Additionally, being a flammable gas, it carries flash, explosion, and fire risks. If stored at −33 ºC as a cold liquid, ammonia also presents a cold-burn hazard in the event of a fuel system leak. This chapter identifies critical equipment and system-based risk factors associated with ammonia fuel supply systems and ammonia-fueled marine diesel engines. It highlights key equipment and outlines potential risk factors, including toxicity, corrosiveness, stress corrosion, low temperature embrittlement, BLEVE, and flammability.