This article outlines the rationale for, and development of an online support system (OSS) for teachers of mathematics in regional, rural and remote (RRR) Australia as part of an ongoing longitudinal project, "Regional Teachers of Mathematics Networks" (RTMN). The OSS is designed to assist development of interconnected collaborative networks for teachers of mathematics in order to help them develop their professional identity. The article builds on the logic of the broader RTMN project, arguing that the development of a teacher of mathematics identity (ToMI) framework through participation in networked communities of practice (CoPs) is integral to improved practice and teacher retention. Theoretical considerations, framed within the overarching conceptual umbrella of cultural accumulation theory, are provided and relate mathematics CoPs to professional development and its role in the development of a 'localised' teacher of mathematics identity. This framing outlines the importance of an OSS that supports both face-to-face and online (virtual) CoP functions for teachers of mathematics. The article also states the case for a design-based implementation research approach that allows stakeholders to sustain ongoing evaluation and updating of the OSS platform for professional learning exchanges within the ToMI framework.