Introduction: The ICD-11 includes a new grouping for “disorders specifically associated with stress” that contains revised descriptions of posttraumatic stress disorder (PTSD) and adjustment disorder (AjD) and new diagnoses in the form of complex PTSD (CPTSD) and prolonged grief disorder (PGD). These disorders are similar in that they each require a life event for the diagnosis; however, they have not yet been assessed together for validity within the same sample. We set out to test the distinctiveness of the four main ICD-11 stress disorders using a network analysis approach. Methods: A population-based, cross-sectional design. A nationally representative sample of adults from the Republic of Ireland aged 18 years and older (N = 1,020) completed standardized measures of PTSD, CPTSD, AjD, and PGD. A network analysis was conducted at the symptom level. Outcome measures included the International Trauma Questionnaire, the Inventory of Complicated Grief, and the International Adjustment Disorder Questionnaire. Results: Consistent with the taxonomic structure of the ICD-11, our results showed that although the four conditions clustered independently at the disorder level, the specific symptoms of PTSD, CPTSD, PGD, and AjD clustered together very strongly but more strongly than with symptoms of the other disorders. The majority (61%) of the variation in each symptom could be explained by its neighboring symptoms. The strongest transdiagnostically connecting symptom was “startle response.” Discussion/Conclusion: Mental health professionals caring for people who have experienced a range of stressors and traumatic life events can be confident in diagnosing these conditions that have clear diagnostic boundaries. Interventions addressing stress-associated disorders should be based on diagnostic assessment to ensure close fit between symptoms and treatment.