Pinene, a major constituent of pine tree oil, was cationically polymerized to generate a high-molecularweight polymer and then subsequently hydrogenated via metal catalysts to give a high-performance, biobased cycloolefin polymer with an alicyclic backbone. To obtain the high-molecular-weight polymer, the controlled/living cationic polymerization of (À)-b-pinene was investigated by an initiating system, consisting of a protonic acid, a Lewis acid, and an added base, along with an incremental monomer addition technique. Among the various systems, the RCl/EtAlCl 2 /Et 2 O system gave a high-molecularweight poly(b-pinene) (M w > 100 000). The catalytic hydrogenation of the obtained high-molecular-weight poly(b-pinene) was examined using various metal catalysts, among which Pd/Al 2 O 3 enabled the quantitative hydrogenation (>99.9%) of the unsaturated C]C group in the repeating unit under mild reaction conditions (1.0 MPa pressure of H 2 ). These reactions could be performed even at relatively large scales to produce several hundred grams of the polymer, which can be then processed through injection-molding. The synthesized bio-based cycloolefin polymers demonstrated promising potential properties as high performance optical plastics with good processability, low density, high optical transparency, low birefringence, non-hygroscopicity, high mechanical strength, and excellent thermal properties.