Driven by the growing interest in coupled processes in fractured media, the International Conference on Coupled Processes in Fractured Geological Media: Observation, Modeling, and Application (CouFrac) was established and chaired by Jonny Rutqvist from the Lawrence Berkeley National Laboratory. The first conference was held in Wuhan, China in 2018 with over 100 presentations including numerical methods, in situ tests, laboratory experiments, and applications to different subsurface engineering activities involving coupled processes. In this special issue, presentations focused on numerical modeling of microscale (micron to centimeter) to macroscale (meter to kilometer) thermal-hydromechanical-chemical (THMC) coupled processes in fractured media were invited to develop full-length peer-reviewed research manuscripts.