approaches are efficient, the olefinic monomers are limited to strained cyclic olefins or special methyl/ethyl-capped acyclic cisdienes. The use of simple terminal acyclic dienes in the selective construction of cis-polyalkenamers remains elusive, despite that this classic type of monomers is not only structurally diverse but also readily available. Hence, it would be highly desirable if cisselective ADMET polymerization of terminal dienes could be realized with the same degree of stereochemical accuracy as previous studies using cis-substrates, which would streamline the production of a wide array of stereocontrolled polymers for diverse applications. The desired cis-selective ADMET requires the selective construction of cis-double bonds between terminal alkenes during polycondensation. Among several classes of stereoselective metathesis catalysts, the cyclometalated ruthenium carbene catalysts were first discovered by the Grubbs group, 7a which quickly expand to a family of catalysts with different chelating structures, NHC backbones, aryl side arms, and anionic ligands. These catalysts have been well explored for cis-selective CM and ROMP with broad compatibility, and a proposed cis-selective ADMET would share a similar mechanistic profile as cis-selective CM, with the olefin substituents pointing away from the NHC side arm during side-bound cycloaddition/reversion and resulting in cis-olefin configuration. However, additional requirements are necessary to facilitate the achievement of both high cis selectivity and satisfactory molar mass in cis-ADMET (Scheme 1b). First, since the Ru-carbene catalyst releases a non-diene olefin (typically a substituted styrene) after the initial catalytic cycle, a sufficiently low catalyst loading with a high turnover number (TON) is preferred for both practicality and a high molar mass. Second, it is often observed that cisselectivity drops significantly in late stages of CMs (e.g., >90% conversion of terminal double bonds), potentially due to the accumulation of decomposed organometallic species and/or increased reprocessing of generated cis-olefins. Therefore, the desired catalyst for cis-ADMET should be able to not only induce high kinetic cis-selectivity during bond formation but also maintain it while pushing the reaction towards almost full conversion. Interestingly, if the catalysts can also perfectly distinguish the reactivity of terminal and cis-olefins from that of main-chain trans-olefins, linear trienes containing embedded trans-double bonds could potentially serve as an effective monomer. This may enable the formation of an alternative cis-trans main-chain configuration that is difficult to access conventionally. Here, we report cis-selective ADMET polymerization of terminal acyclic dienes, which exhibits a broad scope among functionalized skeletons and a high cis-selectivity of up to 99%. We also showcased the convenient synthesis of cis-atrans polyalkenamers from triene monomers and the full degradation of one of these polymers using G2 (Scheme 1c).