The fifth Itzulia Women opened with 121.3 km out of and back into Zarautz, and the day was defined from the start by cold, rain and almost constant climbing — 2,539 m of elevation packed into a short route. Ashleigh Moolman-Pasio was missing from the start line, and the early kilometres passed without major attacks before the gradients and the conditions began to do the selecting.

With the final ascent of Garate cresting just 7.7 km from the line, the race was always likely to fracture late, and it did. Repeated splits on the climbs and a technical run back into town whittled the front to a small group, and Mischa Bredewold — runner-up in each of the last two editions — timed the reduced sprint perfectly to beat Yara Kastelijn and Riejanne Markus. Lauren Dickson took fourth and Antonia Niedermaier crossed two seconds later in fifth after an aggressive ride.

The stage immediately put Bredewold in the leader's jersey, but with only seven and eight seconds back to Kastelijn and Markus, the opening day signalled how tightly contested the three days would be.

Bredewold leads after stage 1 with Kastelijn at +0:07, Markus at +0:08, Dickson at +0:11 and Niedermaier at +0:15. The gaps are small enough that bonus seconds and a single late split could overturn the order on either of the remaining stages.