LONDON — No longer a sideshow, women’s soccer has stepped into the spotlight.

The sport will hope to further establish its growing appeal on Sunday as millions prepare to watch the reigning world champions, the United States, take on the reigning European champions, the Netherlands, in the World Cup final.

The game kicks off at 5 p.m. local time (11 a.m. ET). Tickets for the stadium in Lyon, France, are sold out.

This World Cup has been widely popular with fans and nonfans alike, setting viewing records, and organizer FIFA expects to reach 1 billion viewers by the end of the final.

For some, it marks the point women’s soccer escapes the shadow of the more popular and lucrative men’s game.

Jane Purdon, chief executive of the U.K.-based Women in Football nonprofit, said the last few years had seen increased commitment and investment in the sport.

“While women’s football has been highly enjoyable as a spectator sport for many years, there is no doubt that this World Cup is showing us that the quality has risen yet again,” she told NBC News.

Increased commitment from broadcasters, with many allocating prime television time to Women’s World Cup games, has had a major effect, she said.

“So what we have is a conjunction of improving standards making an entertaining, skillful spectacle, and viewers having easy access to the games," Purdon said.

The United States will start strong favorites for the final after a dramatic 2-1 victory over England in the semi finals.

Along with plenty of on-field drama, U.S. star Alex Morgan sparked debate in the media with a pointed tea-sipping goal celebration.

But this World Cup, fans haven't needed any encouragement to tune in.

The semi final between the U.S and England reached a peak audience of 9 million viewers on Fox and its streaming platforms, with a further 1 million viewers watching on Telemundo.

In the U.K. the match was the most watched television program of the year so far, with a peak audience of 11.7 million.

The other semi final broke the record for women's soccer viewership in the Netherlands, with nearly a third of the entire population of the country tuning in to watch them beat Sweden 1-0.

Records have been falling match after match.

TF1, France’s rights broadcaster, also said the national team's quarter final loss to the United States was the most watched program on French TV so far this year, attracting 10.7 million viewers, or just over half of the total viewing audience.

Meanwhile, France’s earlier round of 16 win over Brazil attracted the biggest single television audience for a Women’s World Cup match ever — with a total of 35.2 million people watching in Brazil.

And in Italy, 7.3 million viewers watched the team take on Brazil. The previous high saw just 202,844 tune in for the Japan versus the U.S. final at the 2011 World Cup, according to FIFA.

The total viewership is still way behind the men’s World Cup, which was seen by more than 3.5 billion viewers last year, but it’s growing fast. The 1 billion viewers expected this year is a big increase on 2015 when 750 million watched the action on TV and 86 million tuned in online or their mobile devices.

Alex Morgan of the U.S. celebrates scoring their 12th goal with Megan Rapinoe in a game against Thailand in Reims, France on June 11. Christian Hartmann / Reuters

Sunday will be a busy day for international soccer.

Brazil faces Peru in the final of South America's men's championship in the afternoon.

The U.S. men's national team then takes on Mexico in the CONCACAF Gold Cup final Sunday night, a scheduling decision that has prompted some criticism.

“It’s ridiculous, and disappointing, to be honest,” U.S. women's star Megan Rapinoe told CBS News.

Fans aren’t just watching at home, though.

Thousands of American supporters traveled to France to watch their team.

“It’s just so exhilarating,” Lena Cooley, the head of the Spokane, Wash. chapter of the American Outlaws fan club, told NBC News in Paris last week.

The sport has come a long way since she was a child and was told by a coach that girls shouldn’t be playing soccer, said Cooley, 53, who wasn’t dissuaded and went on to become the first female licensed referee in Idaho.

“I’m now watching the women out-score the men, they bring in more money than the men. It’s like, yeah guys, it’s time now,” she said.

Aside from the growth of the sport in general, this has simply been a wildly entertaining tournament.

Last-minute wins, controversial decisions from officials using new video review technology, some eye-catching goals and on-pitch drama have added to the momentum and expectation.

History was made by the U.S. team’s crushing 13-0 defeat of Thailand — the largest margin of victory in either the men’s or women’s World Cup.

“If you have a World Cup with big incidents, late goals and drama, it’s only going to help,” lead soccer writer and editor with NBC Sports Joe Prince-Wright said.

NBC Sports: 2019 Womens's World Cup coverage

Prince-Wright added that a drastic improvement in the quality of the women’s game — the result of increased funding from big soccer clubs such as Manchester United and Real Madrid in their women’s teams — had also played a major role in its growing popularity.

“It has taken them a while for whatever reason to figure out that it’s a big deal and they should really be pumping money into it,” he said.

Off-the-pitch drama has boosted the sport’s profile, too. One of the stars of this tournament, U.S. co-captain Meghan Rapinoe, became the target of critical tweets by President Donald Trump after a video emerged of her saying she would not visit the White House if the team was invited.

But there is still a lot of work to be done, Prince-Wright said.

Not all players at this World Cup are full-time professionals, with many still lacking funding and support to make a career out of it.

FIFA doubled total prize money for the 2019 Women's World Cup from $15 million to $30 million, but this is a fraction of the $400 million received by the players in the men’s tournament last year.

Then there's the fact that the tournament's final will be held the same day — July 7 — as the Copa America and Gold Cup soccer finals — something officials have chalked up to "an error."

Still, Jane Purdon says she hopes national associations and existing male professional clubs will keep backing the women’s game.

“They should also look at how the huge wave of interest in the game can translate into greater commercial revenue,” she said.

“For the most part, it’s been a hugely positive World Cup,” Prince-Wright added. “And that’s not just the TV or attendance.”