Abstract Metastatic breast cancer (MBC) remains an incurable disease and is the cause of nearly all deaths from breast cancer. Several barriers prevent efficient research into various questions about living with MBC. A key unmet need is a national database for MBC patient-reported outcomes, which does not exist anywhere in the world. Furthermore, compartmentalized data prevents broad collaborative efforts. Treatment patterns and responses, survival times, and metastatic patterns are not documented systematically and remain unavailable. Large-scale data extraction is challenging, and expensive, and electronic medical records do not provide information regarding patient experiences. Methods: MBC Connect™ was created to help overcome these barriers. MBC Connect, which is sponsored by the Metastatic Breast Cancer Alliance, is a multi-national registry of participant reported information about their experience of MBC. MBC Connect allows MBC patients to voluntarily provide information about their disease, treatment outcomes, and experience of living with their disease so that researchers can gain insight into unmet needs in MBC. MBC Connect has three main goals: 1. Establish an interactive registry of patient-entered, de-identified data for MBC. 2. Create an open-access portal for researchers to study these data. 3. Create a connection between investigators of clinical trials and clinical research studies and registered users who may be interested in clinical trials. Results: MBC Connect collects, via the use of a mobile app (on a smartphone or tablet, iOS and Android compatible) or via a website for desktop users, participant consent, general patient characteristics and demographics, disease characteristics, genetics and tumor mutations, treatment history, quality of life data, and clinical trial experience. This information can be provided by patients living with MBC or their caregiver. The data are collected from responses to surveys and via creation of a treatment profile. The data are de-identified and made available on an open-access Researcher portal, allowing them to be used to advance multiple areas of research into MBC, including both medical treatment aspects and quality of life issues. An interactive feature of MBC Connect is that researchers may submit a request for participants to answer additional surveys. Participants may also be notified about clinical trials for which they may be eligible. In addition, participants will regularly receive “Insights,” which are engaging bytes of information related to MBC. Insights can offer general information about the disease, upcoming events, and other facts, or they can be personalized for the participant based on the information he or she has entered the registry. Conclusions: MBC Connect is a novel platform that aims to accelerate MBC research by providing open access to patient-reported, de-identified data about patients living with MBC. The overarching objective of this technologic initiative is to increase patient engagement with the research community. Citation Format: Campbell L, De La Torre K, Williams CE, Mertz SA, Pollastro T, Hutton A, Newby J, Ellis MJ, Iyengar NM, Hurlbert MS. MBC Connect™, an open-access, patient-reported registry of de-identified data from patients living with metastatic breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-15-03.