Stosur, who beat Serena Williams in last year's final, has faced criticism that the win was a fluke, but the 28-year-old denied those claims.
"Even if I don't win the tournament, I don't think it was a fluke anyway," Eurosport quotes Stosur as saying. "Of course you want to come back and do just as well as the year before.
"I have been trying hard and training well and I'm really looking forward to this year's tournament. You don't come back to defend a Grand Slam every year or every tournament, so it's good. It's exciting."
Stosur begins her defence against Petra Martic of Croatia in the first round.