<p>To promote the transition towards a greener and more efficient chemical industry, new starting materials are needed to produce basic chemicals. Using available resources in a new and efficient way contributes towards mitigating global shortages of particular high-priority chemicals. To address this issue, the low-temperature oxidation of organic matter in different oil shales (OSs) was studied. Oxidation has proven to be an effective way to transform the organic matter in oil shale to value-added products, mainly dicarboxylic acids (DCAs). As this procedure has been effectively implemented on Estonian oil shale, it was expanded to oil shales of different geological origin in an innovative way—by using microwave-assisted oxidation. This paper presents the preliminary mapping of DCA production potential of oil shales from Estonia, the USA, Brazil, Jordan, Kazakhstan, and Syria by using microwave-assisted oxidation. Due to variations in the organic matter structure, the results were presented in relation to total organic carbon (TOC) content. To remove the possible effect of carbonate minerals, one set of the samples was demineralized using formic acid. The preliminary results showed that the proposed method was applicable to different oil shale types, despite not being optimized for individual samples—the reaction was carried out under standard conditions. All samples exhibited a carbon conversion of over 70%, some even more than for the Estonian sample. Even samples with lower conversions demonstrated a high DCA production potential, yielding over 30% DCA/TOC. The lowest yield was obtained for the Syrian sample. The preliminary results show that there is remarkable potential for DCA production from oil shales of different geological origin.</p>