For the first time, a systematic investigation of cluster radioactivity in all even-even naturally occurring isotopes is performed by employing the universal decay law (UDL). Based on the calculated half-lives and the adopted criterion T1/2UDL<1030 yr, twelve α -emitting candidates are suggested, with 176Hf being the shortest-lived case (T1/2UDL=2.79×1018 yr). The systematic analysis presented in this work reveals that: (1) the known and predicted natural α emitters below Z=82 serve as a stringent benchmark for semiempirical decay laws in the extremely low- Q regime, and (2) naturally occurring isotopes offer a distinct advantage in rare-event searches, despite their much longer expected half-lives than those of non-natural isotopes. For heavier cluster decays, among those nuclei with N ≤ 126, only the doubly magic 48Ca emission from 186Os gives a half-life within the 1030-yr limit. In contrast, for 230,232Th and 234,238U with N > 126, the T1/2UDL values for many cluster-emission channels fall within this limit. These findings provide promising candidate cluster emitters among naturally occurring isotopes and therefore motivate future experimental searches.