Comprehensive Summary. (±)-Atrachinenins A—C (1—3), three meroterpenoids possessing novel C skeletons, were isolated from the rhizomes of Atractylodes chinensis. (±)-Atrachinenin A (1) possesses an unprecedented cage-like skeleton with a fused 6/6/5/5 tetracyclic system (decahy-dro-1,5:4a,7-dimethanobenzo[7]annulene), which may be formed by the intermolecular cyclization of (±)-atrachinenin C (3). Compared to 1, (±)-atrachinenin B (2) features an additional unique five-membered peroxyl bridge ring to form a complex 6/6/5/5/5 cyclic ring system. Their structures and absolute configurations were elucidated by HRESIMS, NMR spectroscopic data, ECD calculation, and X-ray diffraction. A plausible biogenetic pathway was proposed. Compound 1 exhibited potential TGF-β inhibitory activity at 25 μmol/L.