The chapter will explore the impact of de-carbonization and the use of alternative fuels in the maritime sector, with the aim of highlighting how ports and shipping are changing their strategies towards a zero-carbon perspective, implementing various initiatives aimed at modernising their infrastructures based on the advent of so-called Green Ships and new Green Ports models (ports as zero-emission ecosystems, where competitiveness and sustainability processes can be improved). The maritime sector’s environmental footprint is certainly rather small compared to the huge volumes of goods transported around the world (90% of international trade travels by sea), but nevertheless the decarbonization of shipping is on the priority list of both the United Nations, through the IMO (International Maritime Organization), and the European Union. The green transition in shipping undoubtedly presents many opportunities, but it is at the same time a complex path due to a number of geopolitical, technical and logistical implications, including the presence of the necessary storage and distribution infrastructure in ports and terminals. Making ‘green-oriented’ choices in a scenario characterized by several unknowns is a far-reaching challenge that needs to be tackled with synergy between the various players in the maritime and port cluster.