Amid growing global environmental challenges, the maritime industry is actively adapting to new requirements to reduce emissions and improve energy efficiency. The International Maritime Organization (IMO) is setting strict standards for the reduction of greenhouse gases, primarily CO2, which is stimulating the introduction of new technical solutions on ships. The purpose of this article is to review modern waste heat recovery technologies, assess their efficiency and environmental benefits, and identify technical and operational limitations that affect the feasibility of their implementation in maritime shipping in the context of the IMO’s strategy to decarbonize the industry by 2050. One of the most promising areas is the use of waste heat, which is traditionally lost to the environment without being reused. Waste heat recovery systems allow excess thermal energy to be converted into useful electrical or mechanical energy. The most researched technologies in this area are Organic Rankine Cycle, Kalina Cycle, and Turbocompound systems. They can provide fuel savings of 3–7% while reducing greenhouse gas emissions and improving the overall energy efficiency of the ship.