This is a game-changer.

Transgender women will be barred from competing in the Olympics — starting in the 2028 Los Angeles games — in a groundbreaking policy decision hailed as a “huge” win for women’s sports.

The move was announced Thursday after the International Olympic Committee (IOC) came to an agreement it said “protects fairness, safety and integrity in the female category.”

“Eligibility for any female category event at the Olympic Games or any other IOC event, including individual and team sports, is now limited to biological females,” said the IOC, which will enforce the ban with a once-in-a-lifetime gene screening.

The decision falls in line with President Trump’s 2025 “Keeping men out of women’s sports” executive order, which decreed that any athletic organization allowing biological males to compete in female sports would have federal funding rescinded.

That order raised questions about the fate of the 2028 games – which have been scheduled since 2017 – as the IOC previously let each sport decide whether to allow transgender women to compete, possibly jeopardizing critical event funding.

Several Olympic sports already banned trans athletes, though not all – in the 2020 Tokyo games, a biological male competed on the New Zealand women’s weightlifting team.

Exactly how many people – if any — might be affected by the new ban during the 2028 Los Angeles games remains unclear. There were no trans competitors in Paris’ 2024 summer games.

The ban will be enforced by a “one-time SRY gene screening,” which checks a person’s chromosomal makeup to determine if they are biologically male.

“The IOC considers that SRY gene screening via saliva, cheek swab or blood sample is unintrusive compared to other possible methods,” the IOC said.

“Athletes who screen negative for the SRY gene permanently satisfy this policy’s eligibility criteria for competition in the female category,” it added. “Unless there is reason to believe that a negative reading is in error, this will be a once-in-a-lifetime test.”

People determined to be biologically male will be allowed to compete in male categories.

But the ban will also apply to women who have a condition known as differences in sex development (DSD), in which they are biologically female but also have male-level testosterone levels, such as champion South African runner Caster Semenya.

Individuals like Algerian boxer Imane Khelif – a woman who also has male SRY genes, and whose participation in the 2024 Olympics sparked controversy – will also be blocked from competing.

“With the exception of athletes with a diagnosis of CAIS or other rare DSDs that do not benefit from the anabolic and/or performance-enhancing effects of testosterone, no athlete with an SRY-positive screen is eligible for competition in the Female Category,” the IOC guidance said.

The decision was “led by medical experts,” according to IOC president Kirsty Coventry, who said researchers had determined that male-level testosterone provided indisputable advantages to competitors in women’s categories.

“At the Olympic Games, even the smallest margins can be the difference between victory and defeat,” Coventry said, according to the BBC.

“So it is absolutely clear that it would not be fair for biological males to compete in the female category,” she added. “In addition, in some sports it would simply not be safe.”

Critics of trans athletes in women’s sports celebrated the IOC decision.

“Obviously this is a win for team sanity,” outspoken sports activist Riley Gaines said on social media, adding that cheek swab gene test would be far less invasive than performance enhancing drug tests that are already mandatory across many sports.”‘Trans women’ haven’t been banned from women’s sports. Men have. Hope this helps!” she wrote on X.

Jennifer Sey, a former member of the US women’s national artistic gymnastics team, also applauded the game-changing ruling.

“This IOC does the right thing and implements sex testing. At the LA Olympics, women’s sports will be women only,” Sey wrote on X. “This is huge. Well done IOC.”

But not all were on board – runner Semenya accused the IOC of caving to political pressure.

“It does not smell of science. It smells of stigma. It was not born from care for athletes. It was born from political pressure,” she said.

New York’s Nassau County Executive Bruce Blakeman also hailed the decision, noting that his county was the first in the nation to ban trans women from competing in women’s sports.

“It started in Nassau County, now the whole world is following suit,” he said. “As County Executive, I was the first to ban biological males from competing in women’s sports, even as Governor Kathy Hochul and Attorney General Tish James called me ‘transphobic.’ The International Olympic Committee’s decision today is a victory for women and girls across the globe.”