Aussies young and old are being urged to "make their mark" by raising awareness and support for wounded veterans in the countdown to Prince Harry's Invictus Games in Sydney later this year.
Games ambassador and Paralympic gold medallist Curtis McGrath is leading the charge, calling on people to set themselves a goal - big or small - and do something in their community to "let our wounded warriors know we're behind them".
"This is a moment in time for us to all come together as a nation and actively demonstrate our support for our defence community," said McGrath, who lost both his legs while serving with the Australian Army in Afghanistan in 2012.
Hundreds of people are expected to join him on a "walk and talk" around Sydney Olympic Park on Sunday to launch the Make Your Mark Down Under campaign.
The event marks 250 days until the Games open in October, when more than 500 competitors from 18 nations will compete in 11 sports.
The campaign was inspired by Prince Harry's call to action during the closing ceremony of last year's Games in Toronto, where he famously made his first public appearance with bride-to-be Meghan Markle.
"Let the examples of service and resilience you have seen, inspire you to take action to improve something - big or small - in your life, for your family, or in your community," he said.
Games chief executive Patrick Kidd said the campaign was all about encouraging Aussies to do something they wouldn't otherwise do, from taking part in a sporting competition to making a quilt.
"You're doing it for some people other than yourself and you're trying to have an impact in your community by being active and being connected," he told AAP.
"And it's equally applicable to people who are young, old, middle-aged. It's about getting them to get off the couch and get them to focus on people other than themselves."
The first Invictus Games were held in London in 2014 after Prince Harry founded the Paralympic-style, multi-sporting event for wounded and sick defence force veterans.
More than 70 Australian veterans are expected to compete in Sydney, where sailing will be included for the first time.
Those hopeful of winning a spot on the team are currently taking part in training camps.