Shipping decarbonization will require a portfolio of levers covering both fleet efficiency and alternative fuels. Shipping companies need to work out which of those levers to pull, in a combination that makes economic sense. Specific pathways are still uncertain, and the industry players face tough choices around retrofitting, buying new vessels, and securing green-fuel bunkering supply. There is no one-size-fits-all strategy, but the most suitable course of action will have to be defined based on individual ambitions, boundary conditions and operational needs. This is what the book Maritime Decarbonization Practical Tools, Case Studies and Decarbonization Enablers is all about: exploring the available options for a commercially viable decarbonization path for the maritime sector in the decades ahead. The book also presents different perspectives on how regulatory compliance can be turned into a competitive advantage through the use of available technologies.