AIMS: To assess if the risk of all-cause mortality increases in people with type 1 diabetes (T1D) with increasing number of severe hypoglycaemia episodes requiring hospitalization. MATERIALS AND METHODS: We conducted a national retrospective observational cohort study in people with T1D (diagnosed between 2000 and 2018). Clinical, comorbidity and demographic variables were assessed for impact on mortality for people with no, one, two and three or more episodes of severe hypoglycaemia requiring hospitalization. The time to death (all-cause mortality) from the timepoint of the last episode of severe hypoglycaemia was modelled using a parametric survival model. RESULTS: A total of 8224 people had a T1D diagnosis in Wales during the study period. The mortality rate (95% confidence interval [CI]) was 6.9 (6.1-7.8) deaths/ 1000 person-years (crude) and 15.31 (13.3-17.63) deaths/ 1000 person-years (age-adjusted) for those with no occurrence of severe hypoglycaemia requiring hospitalization. For those with one episode of severe hypoglycaemia requiring hospitalization the mortality rate (95% CI) was 24.9 (21.0-29.6; crude) and 53.8 (44.6-64.7) deaths/ 1000 person-years (age-adjusted), for those with two episodes of severe hypoglycaemia requiring hospitalization it was 28.0 (23.1-34.0; crude) and 72.8 (59.2-89.5) deaths/ 1000 person-years (age-adjusted), and for those with three or more episodes of severe hypoglycaemia requiring hospitalization it was 33.5 (30.0-37.3; crude) and 86.3 (71.7-103.9) deaths/ 1000 person years (age-adjusted; P < 0.001). A parametric survival model showed that having two episodes of severe hypoglycaemia requiring hospitalization was the strongest predictor for time to death (accelerated failure time coefficient 0.073 [95% CI 0.009-0.565]), followed by having one episode of severe hypoglycaemia requiring hospitalization (0.126 [0.036-0.438]) and age at most recent episode of severe hypoglycaemia requiring hospitalization (0.917 [0.885-0.951]). CONCLUSIONS: The strongest predictor for time to death was having two or more episodes of severe hypoglycaemia requiring hospitalization.