Diatoms (unicellular algae) form porous silica walls (frustule) with intricate, hierarchically organized threedimensional (3D) structures with micro- to nanoscale dimensions. This paper presents the fabrication of self-supporting gold microstructures with complex 3D morphologies by using electroless gold deposition onto a diatom silica substrate, followed by the substrate removal by acid dissolution. It was demonstrated that gold diatom replicas with distinct microto nanoscale structures can be created by a simple and scalable process based on electroless gold deposition. Excellent catalytic properties (catalytic rate constant k=23.5±1 × 10-2 min-1) of prepared gold replica catalysts were confirmed for the reduction process of 4-nitrophenol (4-NP) into 4-aminophenol (4-AP) in the presence of NaBH4 as the reductant. This synthetic approach is general and flexible, and it is envisaged that it can be applied for the preparation of a wide range of different metals (Pt, Pd, Ag, Ni, etc.) offering more efficient catalytic, optical, or magnetic properties.