Decarbonization is the process of reducing carbon dioxide emissions to achieve a lower output of GHGs into the atmosphere. It involves the adoption of sustainable low-carbon power and fuel sources. With such a foundational role in global trade and supply chains maritime decarbonization is critical to decarbonizing the global economy. The introduction of several alternative marine fuels and renewable energy is considered an important strategy for maritime decarbonization. Alternative fuels and energy can help achieve low-carbon and zero-carbon emission goals but their use often requires corresponding high-cost technical and operational measures as a safety guarantee. This course aims to give us better knowledge on the possible pathways and possible technologies that will help the shipping sector achieve its decarbonization target. It presents recent studies regarding alternative fuels renewable energy sources the maturity of technologies as well as technical and operational strategies to reduce fuel consumption.