Since the beginning of 2025, France has experienced an unprecedented early spread of indigenous chikungunya cases, primarily in metropolitan regions. Nearly 53,750 biologically confirmed cases have been reported in Réunion, a French overseas department, where the virus remains epidemic. In mainland France, the first indigenous case of chikungunya in 2025 was detected in La Crau, Var department, in mid-June. This was followed by a second case in Prades-le-Lez, Hérault department, marking the earliest recorded indigenous transmissions of chikungunya in metropolitan France. Subsequently, additional indigenous cases were identified in Corsica, Bouches-du-Rhône, Gard, and Alsace regions, with a total of 30 cases spread across 12 transmission clusters by mid-July. Notably, 10 cases were concentrated in Salon-de-Provence, Bouches-du-Rhône, prompting heightened alert and mosquito control operations. The rapid spread is linked to the ongoing epidemic in Réunion and numerous imported cases, including travelers from Madagascar. Alongside chikungunya, the first indigenous dengue fever cases of 2025 were reported in Auvergne-Rhône-Alpes, with two cases confirmed in Saint-Chamond, Loire department. Public health authorities have initiated extensive mosquito control and awareness campaigns in affected areas. The World Health Organization has expressed concern over the increasing spread of mosquito-borne chikungunya virus globally. Surveillance data from May 1 to late June 2025 show 645 imported chikungunya cases and 454 imported dengue cases in France. The emergence of indigenous cases as early as June is unusual, as such transmissions typically occur later in the summer months, underscoring the growing public health challenge posed by the tiger mosquito (Aedes albopictus) in France.