Purpose To create the patient-facing component of a patient-centric data-sharing platform that will engage and empower radiotherapy patients to contribute data to research to help propel Big Data initiatives in Radiation Oncology. Methods Following a participatory stakeholder co-design approach, data-sharing was facilitated by developing two new user interfaces in the Opal patient portal app (opalmedapps.com): a Radiotherapy menu and a Research menu. A focus group was held to collect initial patient feedback. Results The Radiotherapy menu presents a customized explanation of a patient’s treatment plan based on their treatment parameters. It also displays an interactive 3D rendering of the patient’s body and planned treatment beams for visualization. Next, the Research menu lists ongoing studies, relevant reference materials, and electronic consent forms. Patients who consent to a given study can answer questionnaires from researchers and receive updates and results about the studies they join through the app. The focus group feedback was overwhelmingly positive. By presenting complex radiotherapy data intuitively, patients will likely be better prepared for their radiation treatments and will be more willing to share their data with researchers. Conclusions By prioritizing patient education and access to data, the data-sharing platform created uniquely fosters a sense of trust between patient and researcher that will empower patients to confidently and enthusiastically contribute their data to research to help further Big Data efforts.