This article presents an epidemiological and virological overview of the influenza epidemic in France during the 2017–2018 season. Method: This assessment is based on a descriptive analysis of surveillance data on influenza or influenza-like illness reported by outpatient medical networks, virological analyses from partner laboratories, surveillance of emergency department visits and hospitalizations coded as influenza, surveillance of severe influenza cases hospitalized in intensive care units, reports of acute respiratory infection (ARI) episodes in elderly care facilities, and mortality data. Results: The influenza epidemic began in early December in mainland France, peaked during the last week of December, and ended in late March, lasting 16 weeks. It exhibited atypical dynamics, with two successive waves caused primarily by the circulation of the A(H1N1)pdm09 virus followed by that of the B Yamagata lineage virus. The epidemic was of moderate intensity in outpatient care but was characterized by a high number of hospitalizations following visits to emergency departments for influenza-like illness (>9,700) and severe cases admitted to intensive care (>2,900). This epidemic was also marked by significant excess mortality, with 13,000 deaths attributed to influenza. Conclusion: The 2017–2018 influenza epidemic, which began early and was exceptionally long, was characterized by atypical dynamics and significant severity, linked to the successive circulation of the A(H1N1)pdm09 and B/Yamagata viruses, against a backdrop of insufficient vaccination coverage and suboptimal vaccine efficacy. Its significant impact on hospitalizations and mortality underscores the severity of the disease and the importance of prevention—namely, vaccination of at-risk individuals, supplemented by barrier measures to limit the spread of the virus among contacts of cases—as well as the utility of early antiviral treatment, particularly in at-risk individuals.