Groth eased past the former world No.1 6-3 6-2 in an upset victory at Pat Rafter Arena, needing just 58 minutes to secure the victory.
The hard-hitting Groth smashed home 14 aces as Hewitt found himself unable to respond to the 27-year-old’s powerful serve.
“It’s a credit to (coach) Ben Mathias and (conditioner) Adam Kellett. I now train specific to what my game is, with a lot of power work,’’ Groth said.
“Lleyton’s one of the champions of the game, but I try not to play the man down the other end. I’ve done the hard work and I really feel like I belong.”
The loss will see Hewitt slip around 35 spots in the world rankings from his current position at 84.
Groth will face Polish qualifier Lukasz Kubot in the next round. He joins fellow compatriots Bernard Tomic, Thanasi Kokkinakis, John Millman and James Duckworth in the second round.
Earlier in the evening, Maria Sharapova ousted qualifier Yaroslava Shvedova 6-0, 6-1.
Photo: Don Emmert/Getty Images.