From Martina Navratilova to Greg Louganis to Sheryl Swoopes, men and women from a variety of sports have openly acknowledged their sexuality, though many others are believed to still be reluctant to come forward.
Collins, a 34-year-old NBA veteran, became the first active player in the four major American professional sports to come out as gay, writing a first-person account posted on Sports Illustrated's website Monday. Collins has played for six teams in 12 seasons, including this past season with the Washington Wizards, and is now a free agent.
"It is hugely powerful when any individual in the sports world, wherever they come from in the world, feels able to come out," said Ruth Hunt, deputy chief executive of the British gay rights organization Stonewall. "The fact that this is a current player adds to the strength of his statement."
Previously, some pro sports athletes waited until after quitting to say they were gay, including former NBA player John Amaechi and former NFL running back Dave Kopay. English soccer player Justin Fashanu committed suicide in 1998, eight years after coming out during his playing career.
Amaechi, a center who played five seasons with four teams, became the first NBA player to publicly come out in 2007, three years after the Englishman's playing career was over. He said Collins spoke with him before deciding to come out and called his decision "ground-breaking" and one that could encourage other gay athletes to follow suit.
"I'm getting tons of messages right now from people talking to me about him, about what he's done," Amaechi told The Associated Press. "I've spoken to a couple of college athletes in the States and a couple of high school athletes who are very good who have been immensely buoyed by this news.
"They feel a weight lifted off them even if they aren't out and they aren't going to come out at this point."
Sports leagues in Britain and elsewhere in Europe have been trying to combat anti-gay bias. But the taboo remains particularly strong in soccer, where there are no openly gay players in Europe's top leagues. Homophobic chants still occur at some games.
"Football is not going to change," Amaechi said. "If it wanted to change it would change. It has the resources to do so. It doesn't want to change."
Amaechi said he has been in touch with soccer players, including in the English Premier League, who are gay but are not ready to go public.
"Many of them are out already," he said. "They are out in the way that most people are out in that people they love and that people who care about them know that they are gay. But random strangers don't know that they are gay."
Fashanu remains the only top-level British soccer player to have come out publicly, acknowledging he was gay in 1990. The former Nottingham Forest and Norwich City striker was found hanged in a London garage at age 37.
According to an inquest, Fashanu left a note saying, because he was gay, he feared he wouldn't get a fair trial in the United States on sexual assault charges. Maryland police were seeking him on charges that he sexually assaulted a 17-year-old boy after a party at his apartment.
Robbie Rogers, a former U.S. national team player who played for Leeds in England's second-tier division last season, went public in February that he was gay, saying on his personal website that "I realized I could only truly enjoy my life once I was honest." He also said he was retiring from the sport.
Anti-gay sentiment in soccer has been expressed in different ways.
Last year, Italy forward Antonio Cassano said he hoped there were no homosexual players on the national team and used a derogatory word to describe gays. Fans of two-time defending Russian champion Zenit St. Petersburg signed a petition saying gay players were "unworthy of our great city." Marcello Lippi, Italy's World Cup winning manager, caused a stir in 2009 when he said he had never come across a gay player and would advise gay players to stay in the closet.
"The NBA is light years ahead of football, there is no doubt about that," Amaechi said.
In the U.S., Kopay, who played for five NFL teams over 10 years, was the first pro athlete to acknowledge his homosexuality publicly when he came out in 1977 after retiring, and wrote a book about it.
Four-time diving gold medalist Louganis revealed he was gay in 1994, a year before announcing he was also HIV-positive.
Swoopes, a WNBA star and three-time Olympic gold medalist, disclosed in 2005 that she was gay.
In tennis, women's greats Navratilova and Billie Jean King came out about their sexuality. Former French player Amelie Mauresmo also spoke about her sexual orientation.
U.S. soccer star Megan Rapinoe came out before she played in last year's London Olympics. WNBA star Seimone Augustus and the league's No. 1 draft pick, Brittney Griner, are some of the more recent female athletes to follow suit.
Glenn Burke, an outfielder for the Los Angeles Dodgers and the Oakland A's in the 1970s, and Billy Bean, a utility player in the 1980s and 1990s, disclosed they were gay after retiring. Burke died of complications due to AIDS in 1995.
Gareth Thomas, a Welsh rugby star, attracted widespread media attention in 2009 when he announced he was gay; he played until he retired in 2011.
"I was like a ticking bomb. I thought I could suppress it, keep it locked away in some dark corner of myself, but I couldn't. It was who I was, and I just couldn't ignore it any more. I'd been through every emotion under the sun trying to deal with this," Thomas said in a recent documentary broadcast on British television.
Orlando Cruz of Puerto Rico came out in October as pro boxing's first openly gay fighter, saying, "I don't want to hide any of my identities. I want people to look at me for the human being I am."
Canadian swimmer Mark Tewksbury came out as gay six years after winning a gold medal in the backstroke at the 1992 Barcelona Games. Former Olympic skiing gold medalist Anja Paerson of Sweden announced last year after her retirement that she was in a long-term relationship with a woman. Australian diver Matthew Mitcham came out as gay before he won the men's 10-meter platform gold medal at the 2008 Beijing Olympics.