The maritime sector, responsible for transporting over 80% of global trade volumes, faces increasing pressure to reduce its greenhouse-gas emissions in line with international climate objectives. Energy Saving Technologies (ESTs) have emerged as critical short- to medium-term mechanisms for improving vessel efficiency, supporting compliance with regulatory instruments such as the Energy Efficiency Design Index (EEDI), Energy Efficiency Existing Ship Index (EEXI), and Carbon Intensity Indicator (CII). Despite their recognised potential, empirical evidence on the global diffusion, integration, and technological readiness of ESTs remains limited. This dissertation provides a comprehensive, data-driven assessment of EST adoption across the global fleet, drawing on vessel-level records from the Clarksons World Fleet Register (WFR), covering 54,992 ships built between 1995 and 2025. The study analyses EST uptake across vessel types, age groups, flag states, size categories, classification societies, and the global orderbook, offering one of the most detailed mappings of real-world technology deployment to date. The study also highlights substantial regional and regulatory disparities, with EU-flagged and IACS-classed vessels exhibiting higher adoption rates than their non-EU and non-IACS counterparts. Results show that hydrodynamic and propulsion-enhancing devices—such as rudder bulbs, bow enhancements, propeller ducts, and pre-swirl stators—dominate current installations, reflecting a preference for mature, costeffective technologies. From the analysis, it emerges that ESTs are also chosen to be applied in combinations, with the majority consisting of hydrodynamic pairings that deliver cumulative efficiency gains beyond those achievable individually. Uptake is strongly linked to vessel age, size, and operational profile, with younger and larger vessels showing significantly higher adoption rates. Notably, the orderbook exhibits a markedly higher integration of ESTs than the in-service fleet, indicating a structural shift toward embedding energy-efficiency measures at the design stage of newbuilds; this trend is further reinforced by the 2035 forecasting analysis, which suggests that EST penetration will continue to expand as generational fleet renewal accelerates, regulatory requirements tighten, and energy-efficiency technologies become increasingly integrated with emerging low- and zero-carbon propulsion solutions. Overall, the findings demonstrate that ESTs constitute a significant and indispensable component of the vessels’ decarbonisation process, regardless of the parallel strategies adopted—such as alternative fuels or operational measures—highlighting the enduring relevance of efficiency technologies in achieving emission-reduction objectives across the fleet.