The electrochemical degradation of Pt/C in commercial proton exchange membrane fuel cells (PEMFCs) is a major challenge that limits their durability and performance. This degradation mainly arises from carbon corrosion, which facilitates the detachment of electrocatalyst particles that are weakly bound to catalyst supports. Herein, unusually robust hollow gyroid morphologies designed for strong electrocatalyst fixation and extensive surface accessibility during oxygen reduction reactions (ORR) are reported. To obtain self-assembled gyroid nanostructures using a poly(styrene-b-2-vinylpyridine) (PS-b-P2VP) block copolymer, a solvent vapour treatment with dimethylformamide, which is highly selective for the P2VP block, is applied. It is discovered that retaining residual solvent in the gyroid-forming P2VP microdomain before carbonization is crucial for forming hollow gyroids with embedded electrocatalysts. These hollow gyroid carbon-Pt (HGC-Pt) nanostructures exhibit a 3.6-fold enhancement in electrochemically active surface area compared to solid gyroid carbon (SGC) counterparts. Based on systematic analyses, this exceptional electrochemical stability is attributed to greatly enhanced surface accessibility derived from the hollow geometry, uniform and robust catalyst embedding, and extensive pyridinic nitrogen doping from the P2VP block.