Let the lady pass, gents.

A champion female cyclist was forced to stop during a prestigious race in Belgium — because she caught up to the male competition that started 10 minutes earlier.

The official reason? The lads were simply too slow.

And beyond the apparent male chauvinism involved, the decision to hold back Swiss cyclist Nicole Hanselmann not only cost her the two-minute lead over her nearest female competitor — she said it “killed” her chances to win the race.

Sports fans were left seeing red after Hanselmann was held back by officials at Saturday’s Omloop Het Nieuwsblad race. The 27-year-old said the decision made her lose momentum and she eventually finished the women’s race in 74th place.

Fans of Hanselmann’s described the move by race officials as “pathetic” and “devastating” and said the decision echoed when race officials tried to stop Kathrine Switzer from running in the Boston Marathon in 1967 — five years before women were allowed to compete.

“We came too close to the men’s so we had to get a neutral time gap again,” Hanselmann told website Cyclingnews at the finish line.

“It was a bit sad for me because I was in a good mood and when the bunch sees you stopping, they just get a new motivation to catch you.”

Hanselmann, a Swiss road champion, built up a two-minute lead just 18 miles into the 75-mile race and was starting to come into view of the men’s competition when organizers held her at a rail crossing.

The event’s official Twitter described the interruption as a “neutralisation” of the women’s race due to the men’s race being “very slow.”

“The race jury just said we had to neutralize the race because we are getting too close to the men,” said Hanselmann. “We could just see the ambulances of the men’s race. I think we stopped for five or seven minutes and then it just kills your chances.”

Still, fans rallied around Hanselmann on her Instagram, hailing her as the true champion of the day.

“I’m still trying to find words for the men who were involved in making that pathetic decision of stopping your magnificent race,” one person wrote on her Instagram page.

Added another: “Reminiscent of when race officials physically obstructed Kathrine Switzer from running in the Boston Marathon in 1967. Women weren’t allowed to officially compete for 5 more years. Keep going Nicole! You’re a heroine! Make history!”

On Twitter, some people asked why the men’s race wasn’t told to wait while the women passed.

“Because the men’s race was deemed ‘more important,’” one woman tweeted. “It’s 2019 and cycling still fails at #genderequity.”

Despite the setback, Hanselmann said she was pleased with her efforts.