The poly(2-vinylpyridine) combining highly isotactic (P m = 0.97) and high-molecular-weight (~10 5 g/mol) was obtained for the first time using novel yttrium bis(phenolate) ether catalysts.These catalysts also showed high activity and tolerance to low loadings. Computational studies and kinetic experiments provided a fundamental understanding of the initiation, propagation, and stereocontrol mechanism governing the polymerization reactions mediated by yttrium catalysts.