The International Maritime Organization (IMO) has established ambitious goals for decreasing greenhouse gas emissions in global shipping. Beyond the regulatory obligations, the maritime sector has an increasing perception that sustainability is not just a matter of compliance but a strategic necessity. Investors, consumers, corporations, and stakeholders are progressively urging the industry to embrace a more sustainable and socially responsible approach. In this context, this study explores the influences on the energy efficiency of ships within the regulatory framework. The energy-efficient hull design, advancements in propulsion systems, the use of alternative fuels, and energy management strategies for promoting sustainable shipping are detailed within a regulatory framework. The study also provides insights into measures that can be applied both in the design and operational phases. Additionally, it discusses the significance of ship design concerning energy efficiency and its impact on the environment, drawing upon numerical data from previous studies and current applications. Based on the analyses, the key findings are summarized as follows: The design of energy-efficient ships is evolving with a holistic approach that considers multiple disciplines and objectives such as risk, safety, life cycle, zero emissions, and efficiency. Hull form design and optimization play a crucial role in enhancing energy efficiency, with advancements in parametric modelling and automated optimization tools aiding in decarbonization efforts. The maritime industry is witnessing a shift towards fully electric or hybrid propulsion technologies, including fuel cells, wind-assisted propulsion, solar power, and efficient battery utilization. While alternative fuels like Liquefied natural gas (LNG), LPG, methanol, ammonia, biofuel, and hydrogen offer promising solutions for IMO regulation compliance, their adoption requires careful consideration of ship design, safety measures, fuel availability, and life cycle assessments. Additionally, effective energy management on-board is deemed essential for achieving low-carbon and sustainable shipping, emphasizing the need for holistic energy management technologies incorporated during the ship design phase.