Carl Nassib is the first player to come out as gay while playing in the National Football League (NFL), saying he agonised over making the announcement for the past 15 years.
The Las Vegas Raiders defensive end, who has played 73 games for three teams in his five NFL seasons, made the historic announcement in an Instagram video.
"I just want to take a quick moment to say that I'm gay," Nassib said.
"I've been meaning to do this for a while now but I finally feel comfortable enough to get this off my chest.
"I'm a pretty private person, so I hope you guys know that I'm really not doing this for attention. I just think that representation and visibility are so important.
The 28-year-old is not the first out player in the professional league, with former St Louis Rams defensive end Michael Sam coming out in college before being the first openly gay player drafted into the NFL, in 2013.
Sam played in the 2014 NFL pre-season, but did not play in the regular season, eventually playing in the Canadian Football League and retiring in 2015 due to concerns over his mental health.
Nassib on Instagram revealed he would be donating $US100,000 ($133,000) to youth suicide prevention organisation the Trevor Project.
He thanked his family and friends for giving him the confidence to come out.
"Right now I am sitting in a moment of gratitude and relief. Sadly, I have agonised over this moment for the last 15 years," Nassib said.
"Only until recently ... did it seem possible for me to say publicly and proudly that I'm gay.
"I am also incredibly thankful for the NFL, my coaches, and fellow players for their support. I would not have been able to do this without them. From the jump, I was greeted with the utmost respect and acceptance."
