This paper reports the demonstration of a reactive, self-destructive template for the facile synthesis of branched Au nanostructures. The template is a three-dimensionally porous lattice of uniform, magnetic Fe nanoparticles self-assembled in situ on the surface of a magnetic stir bar. Upon introduction of AuCl, Au atoms are formed in the voids among Fe nanoparticles due to the galvanic replacement reaction between Fe and Au+. The Au atoms then nucleate and grow into branched nanostructures under the confinement of Fe nanoparticles. As the replacement proceeds, Fe is consumed to gradually reduce the sizes and magnetic moments of the Fe nanoparticles. At a certain stage of the reaction, the template starts to fall apart to automatically release the branched Au nanostructures. We can routinely obtain Au multipods as pure samples via selective dissolution of the remaining Fe nanoparticles with sulfuric acid. The as-prepared Au multipods show strong absorption in the near infrared region and exhibit distinctive oxidative etching behaviors in different acidic solutions due to the presence of crystal defects and lattice distortions.