The maritime industry, a cornerstone of global trade, faces mounting pressure to improve energy efficiency and minimize environmental impact. To address this, a systematic review is proposed to analyze trends and advancements, aiming to improve the energy efficiency of ships. This review comprehensively examines contemporary methodologies and persistent challenges in assessing ship energy efficiency. We analyze recent advancements in ship design and operational practices that promote efficiency gains. Additionally, we explore the evolution of regulatory frameworks and industry standards governing energy efficiency assessment. Key challenges, including data availability, measurement accuracy, and technological limitations, are scrutinized along with potential solutions. This review aims to equip researchers, practitioners, and policymakers with a comprehensive understanding of the current landscape, paving the way for future research and policy initiatives that drive sustainable maritime transportation.