The incidence of early-onset breast cancer (EOBC) has recently been shown to be increasing over time in the US and the UK. Using national cancer registries data including 229,352 BC cases, we show that the incidence rate of EOBC in France increased steadily from 1990 to 2023, rising from 16.1 (95 % CI: 14.7-17.8) to 26.3 (95 % CI: 20.7-33.3) and from 98.7 (95 % CI: 93.8-103.7) to 131.2 (95 % CI: 115.8-148.7) per 100,000 person-years in women aged 30 and 40 years, respectively. This population-based study confirms that the incidence of EOBC is increasing over time in Western countries. Further research is needed to explain this trend, which may have implications for prevention and screening strategies.