In summary, we have developed an efficient cis-selective ADMET polymerization using readily available terminal acyclic dienes. A diverse range of stereo-controlled polyalkenamers could be produced with a high cis-percentage of up to 99%. The use of a bulky cyclometalated ruthenium carbene catalyst at a typical loading of 0.3 mol% is crucial for maintaining high cis-selectivity while ensuring satisfactory molar mass. The catalytic system further allows trienes with centrally located trans-double bonds to serve as monomers, providing convenient access to polyalkenamers with alternative cis-trans configurations. The RCM-depolymerization of a cis-ADMET-generated polymer was also demonstrated. Overall, this work expands the possibilities for precision polymer synthesis and may find further applications in material design.