We report here the ethenolysis of squalene and natural rubber utilizing (NHC)(NHC_ewg)RuCl₂(= CRR’) and Grubbs–Hoveyda complexes. 0.01 mol% [Ru] per double bond are sufficient for extensive squalene cleavage, resulting in the formation of numerous terminal olefins, which were identified by GC/MS. The depolymerization of natural rubber requires 0.1 mol% [Ru] and leads to the formation of various oligomeric isoprenes, several of which (n = 2–6) were isolated and characterized.