Highly uniform single-crystal ultrathin Pt nanowires (UTPtNWs) with a diameter of similar to 1.8 nm and a superhigh aspect ratio of > 10(4) were fabricated using insulin amyloid fibrils (INSAFs) as sacrificial templates. The use of INSAFs to build the UTPtNWs allowed for the preferential exposure of low-energy crystal facets that would be highly advantageous for the methanol oxidation reaction. The UTPtNWs displayed a large electrochemical active surface area of 71.34 m(2)/g, which is much higher than that of a commercial Pt/C catalyst. The UTPtNWs also maintained excellent electrochemical durability under repeated cyclic voltammetry scans. Because of its exciting high electrochemical activity, UTPtNWs is a promising material for the design of next-generation electrocatalysts and would also be useful in sensing, biomedical, and other electrochemical applications.