Meghan, who is expecting her first child with Prince Harry, looked stunning in a fairytale ballgown featuring bird motifs and netting. The Duchess wore her brunette hair loose and to one side.
The gown was in Meghan's favoured palette of black and white.
The embellishments on Meghan’s Oscar de la Renta dress were made by Sarah Esmoingt, a French embellishment designer established in New York who works for Oscar de la Renta and Zac Posen among other designers.
Australian fashion expert Donny Galella declared Meghan's dress a hit.
"The Oscar de la Renta gown is what fashion dreams are made of," Donny told New Idea.
"The Duchess looked incredibly divine."
Oscar de la Renta - whose real name was Óscar Arístides Renta Fiallo - was a Dominican fashion designer.
Born in Santo Domingo, he was trained by Cristóbal Balenciaga and Antonio del Castillo. De la Renta became internationally known in the 1960s as one of the couturiers who dressed Jacqueline Kennedy. He died in 2014.
During the awards ceremony, The Duke of Sussex presented young Australian Jade Hameister with the Young Adventurer of the Year Award — in 2018 Jade, 16, became the youngest person to ski to both the North and South poles.
The Duchess of Sussex also presented Sophia Skarparis with the Young Conservationist of the Year Awards, for her work to ban plastic bags in New South Wales.
The royal couple's arrival back into Australia wasn’t without a minor drama as their plane aborted its landing and conducted a “go-around” in the air.
"Our plane has aborted landing," royal commentator Omid Scobie – who was on board the flight – wrote on Twitter.
"Captain calling it a “missed approach” - there was another plane on the runway that was leaving too slowly. Back up we go."
After the captain conducted a go-around, Meghan and Harry landed safely.