O1link is an iPhone application developed by Sejong Smart City Co. Ltd., available for free in the Travel & Navigation category. This integrated mobility service is part of the Sejong City national pilot project, offering smart mobility reservation and payment services. It combines shuttle demand response, personal mobility, vehicle sharing, smart parking, and Sejong City public bicycles (Eoulling).

The key features of O1link include on-demand shuttle services, personal mobility options, vehicle sharing services, smart parking solutions, and access to Sejong City public bicycles. O1link operates as a Mobility as a Service (MaaS) platform, providing route guidance services based on user location, even when not actively using the app.