AbstractUnsaturated vegetable oils are an attractive renewable feedstock, and the selective cleavage of unsaturated fatty esters is an important transformation in this respect. The efficient and selective cross‐metathesis of methyl oleate with ethylene was achieved under mild conditions with ruthenium‐alkylidene catalysts in toluene and room‐temperature ionic liquids (RTILs) to give two important chemical intermediates, 1‐decene and methyl 9‐decenoate, without double‐bond migration. As recovery of the catalyst is an important target with respect to industrial applications, catalyst recycling studies were also carried out in RTILs with the first‐generation Hoveyda catalyst.