<p>Ab initio techniques have revolutionized the way theory helps practitioners to explore mechanisms governing reactions or properties, and develop new strategies for materials discovery and design. Nevertheless, their application to electrochemical systems remains limited, due to challenges electronic structure calculations face in achieving realistic descriptions of electrified solid–liquid interfaces, including potential and pH control or free energies of barrier configurations. The extension of the scope of simulations to achieve potential control, inherent to electrochemical experiments, is just emerging. In this Review, we discuss approaches to describing electrified interfaces between solid electrodes and liquid electrolytes in realistic environments. By exchanging energy, electronic charge and ions with their environment, electrochemical interfaces are thermodynamically open systems. Additionally, large electrostatic potential and field fluctuations occur on timescales and length scales relevant to chemical reactions. We discuss the key challenges for incorporating these features into ab initio simulations to facilitate broader community use and provide a new level of realism when exploring fundamental electrochemistry from first principles.</p><p></p>