This article presents an analysis of the epidemiological and virological characteristics of the influenza outbreak that occurred in mainland France during the 2025–2026 season.Methods—The descriptive analysis focuses on clinical and virological data from the surveillance of acute respiratory infections (ARIs), including outpatient visits for influenza and influenza-like illness, visits to emergency departments for influenza and influenza-like illness, and hospitalizations following a visit to the emergency department for influenza and influenza-like illness, virological data from hospital laboratories and private medical testing laboratories, and clinical data on severe influenza cases hospitalized in intensive care units. It also includes reports of ARI episodes in long-term care facilities (LTCFs), including senior living communities, as well as all-cause and influenza-related mortality data from civil registry offices and electronic death certificates.Results – The influenza epidemic began in early December (Week 49, 2025), it rapidly reached its peak of activity in urban areas in late December (Week 51 of 2025) and ended in early February (Week 06 of 2026), lasting 10 weeks. Co-circulation of the two influenza A viruses, A(H3N2) and A(H1N1)pdm09, was observed. The epidemic was characterized by low to moderate intensity in primary care, with approximately 1.2 million patient visits, but high intensity in hospitals, with approximately 115,000 emergency department visits, 21% of which resulted in hospitalization, a proportion higher than the average during the five previous epidemics. It also had a significant impact in long-term care facilities (approximately 1,600 reported clusters of influenza cases) and in terms of excess mortality (approximately 12,140 deaths from all causes).Conclusion – The 2025–2026 flu epidemic was marked by an unusual discrepancy between its impact in primary care and that observed in hospitals, long-term care facilities, and in terms of mortality. Overall, it ranks among the most severe epidemics since the last influenza pandemic in 2009. Implementing preventive measures is crucial to protecting at-risk individuals, specifically through vaccination of both these individuals and healthcare professionals. This vaccination must be complemented by everyone adopting preventive measures to limit the spread of respiratory viruses within the population and reduce the impact of the flu on at-risk individuals and the healthcare system.