Launched by the Prince of Wales and the Royal Foundation, , external is a set of resources available online that aims "to make suicide prevention as much a part of sport as warm-up, training and performance".
The project is backed by more than 70 organisations including the Football Association, Premier League, Team GB, British Cycling and a host of leading mental health charities.
"Through my work on mental health, I have met people whose lives have been changed forever by suicide," said Prince William. "But I have also met people whose lives have been saved because someone stepped in to help. "
The 44-year-old Royal, who has previously spoken about his own struggles with mental health issues, said that while he acknowledges the good work being done by current services, too often "initiatives are fragmented" and "support is inconsistent, particularly at a grassroots level".
William added that he hopes On Your Side provides everyone involved in sport who notices someone is struggling the "clear, practical guidance" to help that person find the support they need.
On Your Side is being launched to coincide with World Suicide Prevention Day on 10 September.
It remains the biggest cause of death for men under the age of 50 and the rate remains notably higher among males (17.6 per 100,000 people) than females (5.7 per 100,000).
A promotional video for On Your Side features England men's football captain Harry Kane, F1 driver George Russell and Women's Rugby World Cup winner Rochelle 'Rocky' Clark.
The toolkit will officially be launched at 's Hill Dickinson Stadium, a venue chosen because its construction included a 'talking bench' in memory of former player Gary Speed.
Ex-Wales captain and manager Speed, who also played for , Bolton, and Sheffield United, took his own life in November 2011.
Premier League record goalscorer and Match of the Day pundit Alan Shearer, who was a close friend of Speed, is among the athletes to have given their backing to the initiative.
"For me, this is obviously very personal," said Shearer.
"We can't always know when somebody is struggling, but we can all be better at asking, listening, and helping someone find the right support.
"You don't have to be an expert. You don't have to have all the answers, but I hope that everyone in sport will use the toolkit. "
Prince William said he wants On Your Side to take advantage of sport's "remarkable ability to bring people together".
He added: "In moments of need, the right support can make all the difference. We all have the power to help, and that's why suicide prevention must be an important part of everyday sporting life. "
The National Health Service, the Samaritans and mental health charity Mind were all consulted during the creation of On Your Side.
The Royal Foundation said the project had taken two years to complete and added that, although it was being launched to coincide with World Suicide Prevention Day, the initiative is "not a one-day campaign" and hopes it will have a long-lasting legacy.
If you, or someone you know, has been affected by any of the issues in this article, then support and information is available at BBC Action Line.
