Three-dimensional (3D) periodic nickel micro-structures with a periodicity of 4 μm and high number of structural periods were fabricated by electrodeposition. Macroporous silicon, consisting of periodic arrays of sine-wave modulated pores, was used as a deposition template. It was prepared by electrochemical etching of silicon and subsequent pore widening by multiple oxidation/oxide-removal steps. The pore widening allows to open windows between adjacent pores obtaining a 3D network of interconnected voids embedded in silicon. This structure is then void-free filled with nickel in the electroplating process. The combination of electrochemical etching and electroplating techniques opens a route for the fabrication of large-scale 3D-periodic metallic micro-structures. ; Peer Reviewed ; Postprint (published version)