Stereo-electroencephalography (SEEG) creates unique opportunities for clinical applications, brain-machine-interface (BMI) studies and neuroscientific research. However, all of these directions have been under-explored because the lack of an easy-to-use and multi-functional software to accurately localize the SEEG electrodes in 3D space. In this work, we present, for the first time, an SEEG-specific MATLAB-based toolbox (SEEGview) for electrode localization that identifies 3D coordinates and anatomical information for all SEEG contacts within each individual brain, generates cortical activation maps, and maps SEEG contacts from different subjects into one standard brain model. This article first describes how each of these four functions (3D localization, anatomical localization, cortical activation mapping, and SEEG contact standardization) is implemented through SEEGview. We then present localization results based on SEEG data, thereby demonstrating the high localization accuracy and viability for SEEG research.