From Fanny Blankers-Koen to Megan Rapinoe and Simone Biles, women have been pushing the boundaries of sport and changing perceptions for decades.
Gender equality is a top priority in the modern Olympic Movement.
Indeed, the International Olympic Committee (IOC) states that "sport is one of the most powerful platforms for promoting gender equality and empowering women and girls".
The 2018 Buenos Aires Youth Olympic Games broke new ground by being the first multi-discipline Games to have the same number of female competitors as males.
That initiative was only possible due to the previous tireless efforts of women who fought against discrimination in sport, and it is just the start.
To mark the first International Equal Pay Day, Olympic Channel looks at 10 pivotal people or moments in the fight for female gender equality.
Born in 1911 to Norwegian immigrant parents in Texas, Babe Didrikson was the first superstar woman athlete.
At the Amateur Athletic Union Championships ahead of the Los Angeles 1932 Olympic Games, Didrikson won six events and broke four world records.
With women only allowed to compete in three events at the Games, she won the 80m hurdles in a world record and took javelin gold as well as silver in the high jump.
She remains the only athlete, male or female, to win individual Olympic medals in running, throwing and jumping events.
After the Games, she toured with a basketball team called the Babe Didrikson All-Stars.
Two years later, she pitched in three Major League Baseball exhibition games including two scoreless innings for the New Orleans Pelicans against the Cleveland Indians.
In 1935, she started entering golf tournaments having dabbled with the sport in high school and practised it more seriously after her Olympic success.
Didrikson won the Texas Women's Amateur Open but was denied amateur status due to her playing as a professional previously.
Three years later, she entered the PGA Tour's Los Angeles Open and missed the cut after rounds of 81 and 84.
One of her playing partners was wrestler George Zaharias with the pair enjoying each other's company and marrying 11 months later.
After taking three years out in order to regain her amateur status, Babe Zaharias went on to dominate women's golf like no one before or since with the Associated Press (AP) naming her female athlete of the year from 1945 to 1947.
As well as making the halfway cut at three PGA Tour events against the men, she was a founder member of the LPGA and won a Grand Slam of the three majors in 1950.
In 1953, Zaharias - who was now estranged from her husband and living with fellow golfer Betty Dodd - was diagnosed with colon cancer.
One month after having a tumour removed, she claimed her 10th and final major victory at the 1954 US Women's Open by a massive 12 strokes.
But the cancer returned with a vengeance in 1955 and she died a year later aged 45.
It was not until 2003 that Annika Sorenstam became the second woman to play in a PGA Tour event.
Three more have taken on the men but, unlike Zaharias, none have made the cut.
While Zaharias was not universally liked for her arrogant persona, she also received significant criticism as a woman who excelled in sport with writer Joe Williams saying, "It would be much better if she and her ilk stayed at home, got themselves prettied up and waited for the phone to ring."
Her legacy is unmatched and she was an inspiration to those that came after like Olympic long jump and heptathlon champion Jackie Joyner-Kersee who was Sports Illustrated's greatest female athlete of the 20th century, beating Didrikson into second place.
"She was able to show that if she wanted to be a superstar in basketball, she could. If she wanted to be a superstar in golf, she was. If she wanted to be a superstar in track and field, it didn't matter." - Jackie Joyner-Kersee on Babe Didrikson Zaharias to ESPN
Sport was seen as the preserve of men for many years.
The first modern Olympic Games in 1896 were an all-male affair but 12 women competed in the 1900 Games in Paris.
One prominent sportswriter, John Tunis, reported of the final, "Below us on the cinder path were 11 wretched women, five of whom dropped out before the finish, while five collapsed after reaching the tape."
This was not true as only nine started, all of whom finished, and the women on the ground after crossing the line were merely recovering from their exertions.
Unfortunately, the story fitted the agenda of the male-dominated IOC at the time and Olympic races beyond 200m were banned until 1960.
IOC medical and science director Richard Budgett says of the early Olympic years, "Ideas about society and medicine were very different from today. The medical profession was wrong as well, believing that physical exercise was dangerous for women, and that too much effort would harm their reproductive functions."
As late as the 1940s, it was assumed that childbirth meant the end of an female athlete's career, until Fanny Blankers-Koen came along.
After having a boy in 1942, the Dutchwoman set world records in the long jump and high jump and was in a class of her own in short sprints.
War meant the cancellation of the 1944 Games, and Blankers-Koen gave birth to a girl the following year.
Ahead of the London 1948 Games, she attracted criticism for supposedly neglecting her duties her home.
She was also written off for being 30 years old with British athletics team manager Jack Crump calling her "too old to make the grade".
He could not have been more wrong.
Electing to concentrate on the track, Blankers-Koen won a total of four golds in the 100m, 200m, 80m hurdles and the 4x100m relay.
Earning the nickname 'The Flying Housewife', she received a hero's welcome in Amsterdam and is remembered as one of the greatest of all Olympians.
The numbers of women took off after that although it still took time for them to be permitted to compete in a number of disciplines.
The 21st century has brought greater strides towards gender equality with two traditionally male sports, wrestling and boxing, having their first female Olympic competitions in 2004 and 2012 respectively.
And in 2018, the Buenos Aires Youth Olympic Games made history as 1,893 women and 1,893 men took part.
That push for gender equality continues at Tokyo 2020 with every team requiring at least one man and one woman.
That stretches to the Opening Ceremony with each nation having two flagbearers - one of each gender.
There are also new disciplines and categories in several sports scheduled for Tokyo 2020 and Beijing 2022 to level up the numbers of women and men competing.
Equestrian sports are the only disciplines in the Olympic Games where women and men compete against each other individually.
For the Dane to even make the Games was some feat as she had been paralysed by polio in 1944 while pregnant with her second child aged 23.
She made a partial recovery and despite having no movement below the knees - and needing to be helped onto and off her horse by her husband - Hartel won national titles and took silver in Helsinki.
As he was being assisted with her final dismount, Sweden's gold medallist Henri Saint Cyr memorably carried her to the podium.
Four years later, Hartel won silver again in Stockholm which hosted the equestrian events due to Melbourne's animal quarantine laws.
As well as fighting for gender equality, Hartel also battled for the rights of the disabled and founded Europe's first therapeutic riding centre.
She raised huge sums for polio charities and became a Danish national hero.
Shooting was another sport where the women could take on and beat the men.
The Chinese scored a perfect 200 in qualifying and the semi-finals before hitting 23 of 25 targets in the final for an Olympic record and the gold medal.
Separate women's shooting competitions were inaugurated at Atlanta 1996, but Zhang showed definitively that women could more than hold their own against their male counterparts.
Women's tennis simply would not be where it is without Billie Jean King.
And although she was one of the greats with 12 singles and 27 doubles titles in Grand Slams, she will always be remembered best for her victory in the 'Battle of the Sexes'.
Bobby Riggs, a former world number one in the 1940s and an unabashed "male chauvinist pig", was vocal in his belief that women's tennis was vastly inferior to the men's game.
He claimed that even at 55, he could beat the top female players in the world.
After King has initially declined a match, world number one Margaret Court took up the challenge in May 1973 but was thrashed 6-2 6-1.
Having attracted national fame, Riggs stepped up his taunting and King eventually agreed to a winner-take-all clash for US$ 100,000 in the Houston Astrodome in September.
Playing the best-of-five sets, King was broken to trail 2-3 in the first set but soon raised her game.
She had learned a great deal from watching Riggs' win over Court and had her tactics spot on, keeping her older male opponent on the move.
King eventually won 6-4 6-3 6-3 and, in doing so, raised the profile of women's tennis to new heights with 50 million television viewers in the United States and 90 million worldwide.
The crowd of 30,472 remains the record attendance for a tennis match in the United States.
"I thought it would set us back 50 years if I didn't win that match. It would ruin the women's tour and affect all women's self esteem." - Billie Jean King to ESPN on the Battle of the Sexes
King has remained at the forefront of women's tennis and the push for gender equality as well as being a vocal advocate for LGBT rights.
Having been the first president of the WTA and helped arrange lucrative sponsorship for tournaments, she founded the Women's Sports Foundation whose goal is "to advance the lives of girls and women through sports and physical activity".
Her contribution and legacy in tennis and sport is unmatched with, only yesterday, the Fed Cup being renamed as the Billie Jean King Cup.
The 76-year-old is as busy as ever and told Olympic Channel that equality has always been important to her "because no one likes to be discounted".
"By gender, by colour, by sexuality… no one wants to be discounted. When women get less prize money, it just says we are less. Nobody is less, everyone counts, everyone matters. When you have equality then the inclusion is beautiful. But when you don’t, the feeling is horrible.
"Women have always made less than men, in jobs (away from sport), too. That’s why we want more women in the boardroom, more women in media. We want those leadership positions to reflect what the real world looks like. We need more women in coaching. That’s where Fed Cup is amazing — a lot of the coaches are women.
"It’s very important for everyone to have equality and to feel appreciated and included." - Billie Jean King
Even after Blankers-Koen's exploits, it wasn't until 1960 that women were allowed to run distances in excess of 200m at the Olympic Games.
Later that decade, the Boston Marathon became the focal point of the push for gender equality in athletics.
First run in 1897, the Boston Marathon had been an all-male event and there were in fact no sanctioned women's races beyond 1.5 miles (2.4km) in the United States.
In February 1966, local runner Bobbi Gibb applied to compete in the race but race director Will Cloney's reply stated that "women were not physiologically capable of running 26 miles and furthermore, under the rules that governed international sports, they were not allowed to run".
Having trained as much as 40 miles (64km) per day, Gibb knew she could do it and was determined to prove Cloney wrong.
Her mother dropped her off at the start and, wearing a blue hoodie and her brother's Bermuda shorts over a dark swimsuit, she blended in with the other runners at the sound of the gun.
The men around her soon realised she was a woman but Gibb recalls that they were "supportive and friendly" prompting her to remove her heavy sweatshirt.
She crossed the line in 3:21:40 ahead of two-thirds of the field.
"It was a pivotal point in the evolution of social consciousness. It changed the way men thought about women, and it changed the way women thought about themselves. It replaced an old false belief with a new reality." - Bobbi Gibb on completing the 1966 Boston Marathon
The following year Gibb ran again unofficially, but it was another woman who made the headlines.
Kathrine Switzer had registered for the race through official channels, paying the entry fee and signing her name K.V. Switzer as she always did.
Wearing a start number, unlike Gibb, the 19-year-old journalism student began the race with largely supportive male runners around her.
But race manager Jock Semple was so furious at her being in the race that he assaulted her at the two-mile (3km) point, trying to rip off her race bib and prevent her from continuing.
Switzer's coach and fellow runner Arnie Briggs tried to protect her before her boyfriend, hammer thrower Tom Miller, charged at Semple and knocked him to the ground.
Despite the shock and anger, Switzer kept going and managed to finished in four hours and 20 minutes.
Through Gibb and Switzer's actions, women were admitted to the Boston Marathon in 1972.
Switzer covered Munich 1972 as a journalist and became determined to get the women's marathon into the Olympic Games.
She continued running herself, winning the New York City Marathon in 1974.
But it is in promoting road running that she is best known, launching the Avon International Running Circuit and lobbying the IOC for inclusion in the Games.
In 1981, the IOC voted that the women's marathon be run for the first time at the Los Angeles 1984 Games.
Home athlete Joan Benoit took victory although the race is perhaps best remembered for the sight of Gabriela Andersen-Schiess, struggling with heat exhaustion, staggering to the finish.
Switzer recalled, "I felt scared to death that they would see that and pull the event. They would say woman can't handle the marathon."
Those fears were unfounded as the Swiss runner recovered within hours after taking six minutes to complete the final lap of the Olympic Stadium.
Sport remains a minority activity for women in Middle Eastern and North African countries.
Athletes in majority Muslim countries have faced persecution and abuse for competing without covering their entire body.
While Morocco has been more relaxed than some of its neighbours when it comes to women in sport, very few people could have foreseen a gold medal for Nawal El Moutawakel at the 1984 Los Angeles Olympic Games.
The Iowa State University student had reached the semi-finals of the 400m hurdles at the 1983 World Championships.
And despite the death of her father, her biggest supporter, the only woman in the Moroccan team in Los Angeles took half a second off her personal best to claim her nation's first Olympic gold medal.
Injuries forced her to retire in 1987 but she has continued to push for gender equality in roles with the IAAF (now World Athletics) and the IOC.
“I'm proud that things have changed. The change is slow but it's there. So we will continue pushing.” - Nawal El Moutawakel talking to AIPS
As well as becoming a hero in Morocco, El Moutawakel's achievements were recognised throughout the Arab world.
Boulmerka competed at Seoul 1988 but made her name by becoming Africa's first female athletics world champion in the 1500m in 1991.
While her success was celebrated by most Algerians, Boulmerka was criticised by Muslim extremist groups for showing too much of her body during her races.
She received death threats and had to move to Europe to train.
Despite that unrest and upheaval, she took gold at Barcelona 1992 to become Algeria's first Olympic champion, punching the air as she crossed the line.
"It was a symbol of victory, of defiance. It was to say: 'I did it! I won! And now, if you kill me, it'll be too late. I've made history!'" - Hassiba Boulmerka talking to the BBC about her Barcelona 1992 triumph
Since Fanny Blankers-Koen starred at London 1948, few women had attracted the column inches dedicated to the star men in Olympic competition.
But almost as important as that was the diminutive American's response to her achievements citing her desire to build her own legacy as a woman rather than be compared to men.
"I'm not the next Usain Bolt or Michael Phelps, I'm the first Simone Biles."
Since Rio, Biles has continued to push the boundaries of her sport and of what women can do.
Biles had a row with the International Gymnastics Federation (FIG) last year over her new daring beam dismount consisting a double tuck and a double twist.
The FIG gave it an 'H' rating worth 0.8 points and just one-tenth higher than a full-twisting double tuck.
But according to Biles and many gymnastics followers, the extra twist should have made it worth three-tenths more than a full-twisting double tuck for a 'J' rating and a full point.
The FIG responded by saying that its Women's Technical Committee had taken into consideration "the risk, the safety of the gymnasts and the technical direction of the discipline".
But Biles shot back by telling NBC, “They keep asking us to do more difficulty and to give more artistry, give more harder skills. So we do, and then they don’t credit it, and I don’t think that’s fair. It’s so unfair, because, am I in a league of my own? Yes, but that doesn’t mean you can’t credit me for what I’m doing."
The 20-year-old is determined to make her voice heard and has spoken out about the body shaming she has received over the years including being bullied for having muscular arms.
Biles told People, "I’d be lying if I told you that what people say about my body… how I look like in a dress, leotard, bathing suit or even in casual pants hasn’t gotten me down at times
"I am done competing vs. beauty standards and the toxic culture of trolling when others feel as though their expectations are not met…because nobody should tell you or I what beauty should or should not look like." - Simone Biles
The USA's women's national team (USWNT) has dominated football for the past three decades with four Olympic titles and four World Cup triumphs.
But they have always been paid less than the men's national team which has not enjoyed anything like their success.
Ahead of Rio 2016, five members of the USWNT - Megan Rapinoe, Hope Solo, Carli Lloyd, Alex Morgan and Becky Sauerbrunn - filed a complaint with the country's Equal Employment Opportunity Commission alleging wage discrimination.
A new collective bargaining agreement the following year did little to allay the situation with the team filing a lawsuit against US Soccer ahead of the 2019 Women's World Cup alleging “institutionalised gender discrimination”.
As they retained the title, fans chanted and held banners reading "equal pay!" but the case was dismissed by a federal judge in May with the players now appealing that decision.
As USWNT continues their fights for pay equality, other nations have already got on board.
Norway was the first to announce that women's national team players would earn the same as the men with Australia and New Zealand following suit.
Brazil have also adopted the measures as well as England.
Football is also making strides towards gender equality on the pitch with Yuki Nagasato, a member of Japan's London 2012 silver medal side, becoming the first woman to join a men's football team in her homeland.
The Chicago Red Stars' forward has joined Hayabusa Eleven of the Kanagawa Prefecture League on loan.
Nagasato cited Rapinoe as an influence saying, "It was very inspiring to hear the social message about gender inequality and other messages that Rapinoe was trying to deliver during the World Cup. So I have been thinking about how I can do the same.
"I want to get the message out to the girls who are playing soccer with the boys that women can join the men’s team and challenge themselves."
A year later, she made history by becoming the first female non-goalie to play in a men's league.
Wickenheiser played full-time for Finnish third-division side Halamat in 2003, notching up two goals and 10 assists in 23 games to help them win promotion.
She later played for Eskilstuna Linden in the Swedish men's third division.
Since retiring from the ice in 2017 with four Olympic gold medals, she has continued to break barriers by becoming the Toronto Maple Leafs' assistant director of player development in 2018.
As well as training to be a doctor, she is also a member of the IOC Athletes' Commission and is one of Canada's leading voices when it comes to women in sport.
"No one thinks twice about women in sport, right? Of course a girl can play, we say. But why do we need to say it at all? I look forward to the day when it can go unsaid. Athletes can play. All athletes. Regardless of anything other than their desire to play." - Hayley Wickenheiser speaking to The Kit
Months after her second Olympic triumph, the International Bobsleigh and Skeleton Federation opened up the four-man bob to mixed-gender crews.
In November, Humphries piloted a mixed-gender team to bronze in the Canadian four-man bobsleigh championships to qualify for international races.
Later that month, she and perennial rival Elena Meyers Taylor both competed in the North American Cup and finished second and third respectively in Calgary.
Then in January 2016, Humphries drove an all-female team in a World Cup four-man bob race but their weight disadvantage saw them come in last.
That did not matter to Humphries who has already proved she is one of the greatest drivers - male or female - in her sport's history.
The 35-year-old is now competing for the United States and while her hopes of the four-woman bob being at the Olympic Games have not been realised yet - the monobob is being added for Beijing 2022 - she is determined to keep fighting for its inclusion.
"The women before me had to fight for a lot for me to get where I am so I feel a bit of responsibility. What I would love to see is for me to be the first one to win an Olympic gold medal in women's four-man. But if I'm not, then I definitely want to be able to a major contributor to making that happen for somebody else." - Kaillie Humphries speaking to Yahoo Canada Sports
In September 2018, the World Surf League announced that women would receive the same prize money as the men.
It was a move which came in response to hard lobbying from the likes of seven-time world champion Layne Beachley who had to work a part-time job while she was winning surf events around the world.
She told the Guardian in 2017, "Nineteen years on tour earned me a grand total of US$ 550,000 in prize money. It was up to my generation to challenge the status quo, often requiring us to make enormous sacrifices and endure unacceptable circumstances that no current professional surfer will ever have to experience: sleeping in board bags at contest sites because we couldn’t afford proper accommodation; selling prizes such as bikes to afford the next destination; hitch hiking on the North Shore of Hawaii to get to the next event; buying a dozen pairs of Levi 501s in America to sell in France for a spectacular profit; and of course our favourite term, coined by the boys, 'The waves are sh*t so send the girls out.'"
Beachley's fellow Australian Steph Gilmore said to ABC in 2016, "At the end of the day, we're travelling to the same places, we're putting in as much effort and passion and time and we train as much and we kind of just have to look at it as equals."
Surfing had suffered from something of a sexist image in the past with another Australian, Rebecca Woods, claiming she was dropped by her sponsors for not having model looks or wearing a bikini.
Woods told ABC, "I didn't particularly feel like I wanted to get naked to become more famous."
And the pay equality clamour reached a crescendo when this photo was published after the Ballito Pro Junior Series event in South Africa in June 2018.
It shows Indonesia's Rio Waida with a cheque for 8000 rand and home surfer Zoe Steyn holding a cheque for half that amount.
The subsequent furore on social media increased the pressure on the surfing authorities and WSL made their announcement two months later.
Seven-time world champion Gilmore was one of the voices for pay equality telling Vogue, "In the last couple of years I became more vocal about it and began to really ask the questions and sit down with the WSL and say: ‘Why don’t we have equal pay?’ It seems like such an easy thing to fix.
"The WSL have done so much for the women in so many ways, and all the girls on tour were like: ‘We’re so thankful for everything they’ve done already’, and didn’t want to complain. It’s a female thing, it’s ingrained in us to be like: ‘Oh, that’s okay, we’re doing so good already’, instead of fighting for more.”
Now she is an advocate for pay equality in sport and beyond.
"We had just announced equal prize pay. And I realised, world titles are awesome, but what this stood for meant more. That was badass,” - Steph Gilmore talking to Instyle