The first total synthesis of liangshanone, a hexacyclic ent‐kaurane diterpenoid alkaloid, has been completed. Its intricate cagelike framework was assembled through several key transformations, including an oxidative dearomatization/Diels–Alder (OD/DA) cycloaddition sequence, a tandem alkene cleavage/Mannich cyclization, a Robinson‐type annulation, and an intramolecular aldol reaction. Notably, an