<p>Phase-separated ionogels have emerged as a promising class of functional materials characterized by their unique thermodynamic behavior. In contrast to conventional polymer networks that rely on specific chemical structures, phase separation in these systems stems from the thermodynamic instability of polymer-solvent interactions. This mechanism allows precise control over material properties through a multiscale structural design. Ionic liquids (ILs), which serve as the dispersion medium, play a pivotal role in tuning the lower critical solution temperature/upper critical solution temperature (UCST/LCST) phase behavior of the corresponding ionogels owing to their tunable cation-anion combinations, polarity, and hydrogen-bonding capacity. These features not only facilitate the construction of thermally responsive ionogels but also provide a versatile platform for mechanistic studies. This review systematically explores the formation mechanisms of phase separation in ionogels, emphasizing the crucial influence of the physicochemical properties of ILs and categorizing the key driving forces behind phase separation. It further examined the distinctive effects of phase separation on the surface/interfacial properties, mechanical behavior, and electrical performance of ionogels, incorporating the latest research advances. Finally, the current challenges and prospective research directions for phase-separated ionogels were outlined.</p>