Since the first report in 2015, multiresonant thermally activated delayed fluorescent (MR-TADF) compounds, a subclass of TADF emitters based on a heteroatom-doped nanographene material, have come to the fore as attractive hosts as well as emitters for organic light-emitting diodes (OLEDs). MR-TADF compounds typically show very narrow-band emission, high photoluminescence quantum yields, and small ΔEST values, typically around 200 meV, coupled with high chemical and thermal stabilities. These materials properties have translated into some of the best reported deep-blue TADF OLEDs. Here, a detailed review of MR-TADF compounds and their derivatives reported so far is presented. This review comprehensively documents all MR-TADF compounds, with a focus on the synthesis, optoelectronic behavior, and OLED performance. In addition, computational approaches are surveyed to accurately model the excited state properties of these compounds.