The 118.6 km opener from Saint-Jean-de-Luz to Mourenx was the clearest chance for the sprinters before the mountains, with only two minor classified climbs (Saint-Cyprien and Lay-Lamidou). The decisive move came from Eliška Kvasničková (VIF Cycling Team), who went solo with just under 60 km to go and built her lead to more than three minutes as the peloton hesitated. Katja Verkerk and a small chasing group tried to bridge, while a large mid-stage crash forced several abandons and added to a stop-start feel.

With around 18 km left the gap to Kvasničková was still about 2:15, but Cofidis, UAE Team ADQ, Liv AlUla Jayco and FDJ United-SUEZ committed to the chase — Franziska Koch was prominent in lifting the tempo for Le Net — and the move was reeled in inside the final 11 km. In the reduced bunch sprint Martina Alzini took her first win in three years ahead of Federica Venturelli and French champion Marie Le Net, claiming the first leader's jersey of the race.

Martina Alzini (Cofidis) took the first leader's jersey by winning the bunch sprint, with the GC favourites all safely in the front group and time gaps minimal ahead of the queen stage. The overall picture would be reshaped entirely on the Tourmalet the following day.