Abstract Background Medical deserts represent a pressing public health and health systems challenge. The COVID-19 pandemic further exacerbated the gap between people and health services, yet a commonly agreed definition of medical deserts was lacking. This study aims to define medical deserts through a consensus-building exercise, explaining the phenomenon to its full extent, in a manner that can apply to countries and health systems across the globe. Methods We used a standard Delphi exercise for the consensus-building process. The first phase consisted of one round of individual online meetings with selected key informants; the second phase comprised two rounds of surveys when a consensus was reached in January 2023. The first phase-the in-depth individual meetings-was organized online. The dimensions to include in the definition of medical deserts were identified, ranked and selected based on their recurrence and importance. The second phase-the surveys-was organized online. Finally, external validation was obtained from stakeholders via email. Results The agreed definition highlights five major dimensions: ‘Medical deserts are areas where population healthcare needs are unmet partially or totally due to lack of adequate access or improper quality of healthcare services caused by (i) insufficient human resources in health or (ii) facilities, (iii) long waiting times, (iv) disproportionate high costs of services or (v) other socio-cultural barriers’. Conclusions The five dimensions of access to healthcare: insufficient human resources in health or; facilities; long waiting times; disproportionate high costs of services and; other socio-cultural barriers, ought to be addressed to mitigate medical deserts. The term medical deserts might not be the most appropriate term for defining areas with insufficient access to health services as it excludes essential domains, such as access to public health and preventive services. Key messages • Medical deserts directly and negatively impact the health outcomes of the people living in it. • Medical deserts might not be the most appropriate term for defining areas with insufficient access to medical services, as it excludes public health and preventive services.