Purpose: The recent rise in the incidence of cancer in younger adults has been described in high-income countries. This study aimed to identify cancer incidence trends in France among adolescent and young adult (AYA) population. Methods: All cases of cancer diagnosed in 15-39 years, recorded by all French population-based registries (24% of the population), over the 2000-2020 period, were included. World age-standardized incidence rates (ASR) and annual percentage change (APC) of incidence over time were calculated. Results: We analyzed 54,735 cancer diagnoses in AYAs. The ASR over the 2000-2020 period in 15-39 years was 58.1 per 100,000 (95% confidence interval [CI] 57.0-59.2). ASR was lower in males (47.2 [45.7-48.6]) than in females (68.9 [67.2-70.6]). Incidence per 100,000 differed with age group from the lowest, 20.5 (19.8-21.2) in 15-19 years, to the highest, 130.3 (128.6-132.0) in 35-39 years. Increases in incidence were observed for essential thrombocythemia (APC: 3.33% [1.52-5.16]), Hodgkin lymphoma (HL) (APC: 1.86% [1.21-2.52]), liposarcoma (APC: 3.68% [0.83-6.61]), carcinomas of urinary tract (APC: 3.95% [2.85-5.06]), gastrointestinal tract (APC: 2.62% [1.96-3.28]), and breast (APC: 1.61% [1.22-2.01]) from 2000 to 2020, glioblastoma (APC: 6.11% [3.06-9.26]), and other astrocytomas (APC: 7.41% [5.13-9.75]) from 2005 to 2020. Decreases in incidence were observed for oligodendroglioma (APC: -8.78% during 2005-2020), and other invasive carcinomas (APC: -3.34% during 2000-2020). Conclusion: Increases in the incidence of some AYA cancer types are observed HL, liposarcoma, carcinomas of colorectum, breast, and kidney. Results for central nervous system tumors are still to be confirmed in the years to come. Extensive efforts are needed to identify underlying risk factors responsible for these trends to inform prevention strategies.< Réduire