The Roar missed the finals last season and coach Warren Moon met Austin, who played in the Championship for QPR last season, in London to secure the striker to lead his attack.
"To play abroad is something I've always wanted to do and when the opportunity came up to join this club I was looking to explore it," said Austin, who's understood to have signed a two-year deal.
"I met the gaffer Warren in London and he sold me the project of the football club and it was one I was excited about.
"I want to help the club get back into the top six and on a personal note score as many goals as possible."
Austin notably scored 18 times in his first Premier League campaign with QPR in 2014-15 and earned an England call-up in 2015 without making his debut.
He notched a further 16 top-flight goals and two in Europe while at Southampton to enhance his reputation as a prolific goalscorer.
Not only does Austin give the Roar a high-profile name, Moon is confident the 32-year-old has the drive to shine in the ALM.
"We're delighted to secure a player with such a proven goal-scoring record," Moon said of Austin, who has scored 173 senior league and cup goals. "Charlie has scored goals wherever he's been. From my discussion with him, he comes to us with great ambition to try to hit the 200 mark for his career.
"That says to me that we have a player who is coming here to be successful for Brisbane Roar and who has the hunger to continue doing what he loves best and that's scoring goals."
Meanwhile, the Roar will return to Suncorp Stadium for three games from next season after being based at Redcliffe for the past two campaigns.