Ballast water management is a national and international issue in the shipping industry because of potential ecological hazards caused by the release of ballast water into the marine environment. Although many international standards have been implemented in recent years, technological and practical considerations make the ballast water treatment a major challenge for many shipping companies. In this paper, a novel concept of utilizing ballast water as source water for a multieffect desalination process driven by onboard waste heat to meet the freshwater supply needs is proposed with theoretical analysis and practical considerations. A main engine with a capacity of 7500 kW in a cruise ship can serve as a potential waste heat source for water desalination of 1000 m3/d, which can provide for freshwater needs of 2000 to 4000 ship occupants. This scenario presents an attractive alternative to ballast water management and treatment as well as reducing the nonrenewable energy footprint of onboard water supplies in marine industry.