<p>Electrochemical water splitting is at the heart of green hydrogen generation and plays a pivotal role in the development of the energy transition toward net-zero carbon emissions. Although the thermodynamic minimum required for electrochemical water splitting is as low as 1.23&#xa0;V, the actual voltages employed in electrolyzers for this process are substantially higher than the thermodynamic minimum because of the kinetic overpotentials associated with the hydrogen evolution reaction (HER) and more so the oxygen evolution reaction (OER). Over the years, the performance of electrocatalysts such as platinum and iridium oxide has been the benchmark for electrochemical water splitting because of the thermodynamically and kinetically optimal adsorption and reaction characteristics of these materials. However, the extreme scarcity and associated high cost of these materials have been the major hurdles for the large-scale implementation of these electrocatalysts for electrochemical water splitting. This has led to the progressive development of electrocatalysts for electrochemical water splitting from noble metals and their compounds to earth-abundant transition-metal compounds and more recently to metal-free and biomass-derived electrocatalysts. This review aims at narrating the scientific evolution of electrocatalysts for electrochemical water splitting and the associated thermodynamic and kinetic principles, structure-activity relationships, and performance descriptors for the hydrogen evolution reaction and the oxygen evolution reaction. Special emphasis has been given to the performance of biomass-derived electrocatalysts for electrochemical water splitting in alkaline media and the associated cost benefits for the development of electrochemical water splitting technology in the near future. This review contrasts other literature reviews which center mainly on a specific catalyst family and provides an evolutionary perspective covering noble metals catalysts, transition metals complexes, artificial carbon-based catalysts without any metals, and bio-based electrocatalysts for hydrogen evolution reaction. In addition, the concept of Activity–Stability–Cost trilemma and a six-dimensional performance mapping tool is presented. This review aims at providing a broad overview for beginners and detailed information for researchers in the area of electrochemical water splitting and the associated electrocatalysts for the development of the next generation of electrocatalysts for electrochemical water splitting technology.</p> Graphical abstract <p></p>