Diagnostic journeys begin when patients first present to a healthcare provider for their symptoms and end when they receive the correct diagnosis for these symptoms. In many cases, the diagnosis can be made promptly, but patients with rare, complex, or unusual conditions often embark on odysseys spanning years to sometimes even decades in search of a diagnosis. This prolonged process can often result in excessive costs, preventable medical errors and iatrogenesis, as well as feelings of frustration, abandonment and isolation. To address these issues and facilitate discussion, a shared conceptual framework and vocabulary are needed. Here we propose a framework that partitions a patient's diagnostic journey into three distinct phases related to navigation within the healthcare system: The primary encounter, an initial round of referrals, and subsequent evaluations and second opinions. The three phases of the diagnostic journey are interconnected, and each can be further studied and optimized.