This special issue of Semiconductor Science and Technology on 'Electrochemical Processing of Semiconductor Materials' is devoted to basic and applied research in the multidisciplinary field of porous semiconductor materials. It presents 13 selected and peer-reviewed research articles covering the following three main areas: (i) formation of porous semiconductor structures, (ii) the galvanic filling of pores, and (iii) applications for these porous semiconductor structures. The first part of this special issue focuses on the formation of porous semiconductor structures by diverse processing techniques: electrochemical etching, metal-assisted etching, and stain etching. The second part covers the galvanic filling of pores with a special emphasis on magnetic materials and includes a review of the current status of this field. The fabrication of ZnO nanowires is also discussed. The application section deals mainly with emerging energy applications—Li-ion batteries and solar cells—but also covers optics and catalytic activities of porous semiconductor structures. We thank all of the authors from around the world for their important contributions in the field of the electrochemical processing of semiconductors, and for their particular contributions to this special issue. We also thank the reviewers for their important advice, and we owe special thanks to Alice Malhador, Dean Williams, and their team from IOP Publishing for their exemplary support in organizing and assembling this special issue.