Abstract: With the rising ocean heat content driven by global warming, marine heatwaves (MHWs), as extreme ocean temperature anomalies, have exhibited significant increase in frequency, intensity, and duration, and posed severe threats to global marine ecosystem stability and health. This paper comprehensively reviews recent domestic and international research and systematically synthesizes the evolution of MHWs definitions and classification, driving mechanisms, attribution, and impacts. Through reviewing the evolution of MHWs assessment frameworks, we show that current approaches have advanced beyond early single-SST-threshold criteria to develop multidimensional evaluation systems encompassing intensity classification, spatiotemporal clustering, and comprehensive indices, and markedly improved the capability of capturing large-scale extreme events. Further analysis of physical driving mechanisms reveals the regionally varying contributions of atmospheric forcing and internal ocean dynamics, as well as their modulation by large-scale climate modes. Anthropogenic greenhouse gas emission has been confirmed to be the dominant driver of recent extreme MHWs events, whose occurence probability is expected to increase nonlinearly under future warming scenarios. The review also summarizes the widespread ecological impacts of MHWs, including coral bleaching, seagrass meadow degradation, and loss of genetic diversity, as well as the combined effects of MHWs with typhoons, hypoxia, and ocean acidification. Finally, realizing the limitation that current research mostly focuses on the sea surface, we provide a perspective research frontier extending from two-dimensional surface to three-dimensional subsurface heatwaves, highlighting integrated deep ocean observational networks and high-resolution modeling as critical foundations for understanding subsurface heatwave evolution mechanism and enhancing prediction capability.