The 51st Boucles de la Mayenne opened with a short 5.4 km individual time trial in Laval. Julius Johansen, riding for UAE Team Emirates - XRG, set the fastest time at an average of 49.1 km/h, edging Lidl - Trek's young Swede Jakob Söderqvist by a single second. Oscar Chamberlain (Decathlon CMA CGM) was third at +6, with UAE's own GC card Benoît Cosnefroy fourth at the same +6. Thibaud Gruel and Ivo Oliveira completed the top six at +7.

The prologue did exactly what it is designed to do at Mayenne: seed the general classification within a handful of seconds and hand UAE the early initiative. Johansen took the first leader's jersey and the early points lead; Chamberlain led the youth classification.

Johansen leads from Söderqvist (+1) and Chamberlain (+6), with Cosnefroy fourth at +6 and Gruel fifth at +7 — the entire field bunched inside single-digit seconds heading into two flat sprint-friendly road days and one hilly queen stage that would decide the race.